KRC

Line plots across dimensions of each concept
Line plots across concepts
Tables

Plots across concepts

IncomeStatement

Balance Sheet

Assets

Current Assets

NonCurrent Assets

Liabilities

Stockholders Equity

CashFlow

NetCashProvidedByUsedInOperatingActivities

NonoperatingIncomeExpense

LesseeOperatingLeaseLiabilityPaymentsDue

AccountsReceivable

Tables

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:CommonStockValue	███▇▇▇▄▄▂▂▂▂▂▁▁▁▁▁	1.165	1.165	1.16	1.152	1.152	1.151	1.06	1.06	1.01	1.01	1.007	1.007	1.006	0.988	0.986	0.984	0.984	0.983
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding	█▁	116.917463	116.801384	NA	115.667657	115.539725	107.389575	NA	105.359904	101.809541	101.443179	NA	101.228334	100.150856	99.21361	NA	98.911612	98.827378	98.018157
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic	█▁	116.451931	116.344375	NA	115.226324	115.084897	106.875234	NA	104.841176	100.972355	100.90139	NA	100.676778	99.6917	98.74422	NA	98.352139	98.275471	97.388137
us-gaap:EarningsPerShareBasic	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	0.3	4.27	0.67	0.42	0.17	0.37	0.68	0.41	0.41	0.36	1.59	0.34	0.27	0.36	0.28	0.67	0.3	0.27
us-gaap:EarningsPerShareBasic dei:LegalEntity krc:KilroyRealtyL.P.	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	0.3	4.27	0.67	0.42	0.16	0.37	0.68	0.41	0.41	0.36	1.58	0.34	0.27	0.36	0.28	0.67	0.3	0.26
us-gaap:EarningsPerShareDiluted	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	0.3	4.26	0.67	0.42	0.17	0.37	0.67	0.41	0.41	0.36	1.58	0.33	0.27	0.36	0.28	0.67	0.3	0.26
us-gaap:EarningsPerShareDiluted dei:LegalEntity krc:KilroyRealtyL.P.	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	0.3	4.26	0.67	0.42	0.16	0.36	0.67	0.41	0.41	0.36	1.57	0.33	0.27	0.36	0.28	0.67	0.3	0.26

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Margin from Continuing Operations dei:LegalEntity krc:KilroyRealtyL.P.	▇█▇▇▆▆▆▆▄▄▃▂▂▂▁▁▁	225.983	235.646	229.332	228.314	219.423	221.328	220.235	215.525	200.492	201.202	190.842	186.562	187.072	182.822	177.561	181.534	180.598	NA
Net profit Margin dei:LegalEntity krc:KilroyRealtyL.P.	▇█▇▇▆▆▆▆▄▄▃▂▂▂▁▁▁▁	225.983	235.646	229.332	228.314	219.423	221.328	220.235	215.525	200.492	201.202	190.842	186.562	187.072	182.822	177.561	181.534	180.598	179.308

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:AllocatedShareBasedCompensationExpense	▆▅▃▃█▄▄▂▄▄▆▃▆▁▃▂▂▂	11.2	9.6	7.6	7.8	13.6	8.7	8.4	6.8	8.7	8.8	11.2	8.1	11.5	5.1	7.3	6.4	6.5	6.2
us-gaap:GeneralAndAdministrativeExpense	▄▃▄▂█▂▃▃▃▄▇▂▃▁▂▁▁▁	24.507	21.985	23.085	18.572	38.597	19.01	22.365	22.576	19.857	23.341	33.872	19.277	21.763	15.559	16.831	14.514	14.303	14.933
us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	35.839	497.631	78.642	49.028	19.618	39.817	72.5	43.846	42.194	36.903	160.22	34.4	27.549	36.246	28.529	71.11	31.448	33.525
us-gaap:InterestExpense	▇█▇▆▄▃▃▁▁▁▂▁▂▃▃▄▅▅	21.39	22.334	20.976	19.468	15.884	14.444	13.932	11.635	11.727	11.243	12.436	11.075	12.712	13.498	14.564	16.151	17.973	17.352
us-gaap:InterestPaidNet	█▃▇▃▄▃▄▁▅▁▃▂▄▂▆▄▃▅	29.133	12.387	25.843	10.404	15.459	10.035	15.468	5.13	18.303	4.706	12.522	7.039	15.437	9.699	20.458	15.901	12.771	18.206
us-gaap:NetIncomeLoss		NA	NA	78.642	49.028	19.618	39.817	72.5	43.846	42.194	36.903	160.22	34.4	27.549	36.246	28.529	71.11	31.448	33.525
us-gaap:NetIncomeLoss dei:LegalEntity krc:KilroyRealtyL.P.		NA	NA	79.654	49.728	19.838	40.389	73.74	44.589	42.901	37.508	163.309	34.993	28.015	36.893	29.013	72.402	31.971	34.054
us-gaap:NetIncomeLossAttributableToNoncontrollingInterest	▅█▂▂▂▃▃▂▂▂▄▁▂▂▁▂▁▁	7.041	9.78	4.81	5.043	4.734	5.601	5.422	4.452	5.021	4.891	6.67	3.91	4.206	4.725	4.011	4.378	3.858	3.756
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	35.839	497.631	78.642	49.028	19.618	39.817	72.5	43.846	42.194	36.903	160.22	34.4	27.549	36.246	28.529	66.558	29.833	26.329
us-gaap:NonoperatingIncomeExpense	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▁▁▁	-19.51	436.327	16.405	-17.599	-13.046	-17.572	17.137	-10.874	-3.942	-9.415	127.986	-10.733	-11.941	-13.464	-18.002	-14.625	-16.935	-16.287
us-gaap:NonoperatingIncomeExpense dei:LegalEntity krc:KilroyRealtyL.P.	▁█▂▁▁▁▂▁▁▁▃▁▁▁▂▁▁	-19.51	436.327	16.405	-17.599	-13.046	-17.572	17.137	-10.874	-3.942	-9.415	127.986	-10.733	-11.941	-13.464	21.954	-14.625	-16.935	NA
us-gaap:OperatingExpenses	▆▆▅▅█▅▅▅▄▄▄▂▃▁▁▁▁▁	163.593	164.562	162.285	156.644	182.025	158.338	159.45	156.353	149.335	149.993	151.938	137.519	143.376	128.387	127.019	129.12	128.357	127.997
us-gaap:ProfitLoss	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	42.88	507.411	83.452	54.071	24.352	45.418	77.922	48.298	47.215	41.794	166.89	38.31	31.755	40.971	32.54	75.488	35.306	37.281
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax	▁▁█▁▁▁█▁▁▇▇▇▇▇▆▇▇▆	1.51	0.99	229.332	1.192	1.067	2.695	220.235	3.204	2.863	201.202	190.842	186.562	187.072	182.822	177.561	181.534	180.598	179.308
us-gaap:Revenues	▇█▇▇▆▆▆▆▄▄▃▂▂▂▁▁▁▁	225.983	235.646	229.332	228.314	219.423	221.328	220.235	215.525	200.492	201.202	190.842	186.562	187.072	182.822	177.561	181.534	180.598	179.308

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:Assets	██▇▇▇▇▅▅▃▃▃▂▂▁▁▁▁▁	10434.766	10384.353	10000.708	9984.608	9658.665	9735.147	8900.094	8623.815	8094.721	7883.987	7765.707	7562.236	7384.784	6965.932	6802.838	6838.299	6995.367	6993.665
us-gaap:Liabilities	████▇▇▆▆▅▄▄▃▃▂▁▁▂▂	4741.301	4681.461	4723.387	4732.644	4405.076	4457.632	4329.236	4084.306	3907.818	3700.805	3564.446	3487.317	3320.911	3018.46	2842.522	2942.419	3032.896	3027.524
us-gaap:LiabilitiesAndStockholdersEquity	██▇▇▇▇▅▅▃▃▃▂▂▁▁▁▁▁	10434.766	10384.353	10000.708	9984.608	9658.665	9735.147	8900.094	8623.815	8094.721	7883.987	7765.707	7562.236	7384.784	6965.932	6802.838	6838.299	6995.367	6993.665
us-gaap:StockholdersEquity	██▆▆▆▆▃▃▂▂▂▁▁▁▁▁▁▁	5446.943	5458.245	5029.943	4968.142	4972.291	4992.15	4293.51	4264.649	3915.532	3914.524	3929.907	3804.758	3802.927	3686.859	3700.793	3689.863	3756.469	3759.323

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:CashAndCashEquivalentsAtCarryingValue	▅▆▇█▆▇▁▃▁▁▁▁▁▁▁▁▄▅	519.307	657.819	731.991	849.009	605.012	762.134	60.044	297.62	52.415	49.693	51.604	86.517	50.817	53.069	57.649	64.954	387.616	478.391
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	▅█▄▄▃▄▁▂▁▁▂▁▁▁▁▂▂▃	969.764	1686.578	823.13	865.309	621.312	778.434	76.344	303.92	58.715	55.993	171.034	86.517	50.817	53.069	66.798	244.23	395.865	485.59
us-gaap:AccountsReceivableNetCurrent		NA	NA	12.007	NA	NA	NA	26.489	NA	NA	NA	20.176	17.519	15.144	17.602	16.926	18.626	13.703	13.74

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:FurnitureAndFixturesGross	▃▃▄▄█▁▁▁▁▁▂▂▂▂▃▃▃▃	40.679	40.752	43.367	42.899	53.06	35.776	35.286	36.192	36.466	36.043	36.833	36.717	37.799	38.541	39.686	39.889	39.693	39.371
us-gaap:FiniteLivedIntangibleAssetsNet krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass krc:DeferredLeasingCosts		NA	NA	196.279	NA	NA	NA	185.881	NA	NA	NA	166.1	NA	NA	NA	146.681	NA	NA	NA
us-gaap:FiniteLivedIntangibleAssetsNet krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass us-gaap:LeasesAcquiredInPlace		NA	NA	14.67	NA	NA	NA	26.429	NA	NA	NA	30.352	NA	NA	NA	35.472	NA	NA	NA
us-gaap:OperatingLeaseRightOfUseAsset	█▃▃▃▃▃▃▁▁▁	141.529	95.312	95.523	95.733	95.94	96.145	96.348	83.2	82.647	82.794	NA	NA	NA	NA	NA	NA	NA	NA

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:LongTermDebt dei:LegalEntity,us-gaap:LongtermDebtType krc:KilroyRealtyL.P.,us-gaap:SecuredDebt		NA	NA	253.582	NA	NA	NA	258.593	NA	NA	NA	335.531	NA	NA	NA	340.8	NA	NA	NA
us-gaap:LongTermDebt us-gaap:LongtermDebtType us-gaap:UnsecuredDebt		NA	NA	3700.0	NA	NA	NA	3300.0	NA	NA	NA	2600.0	NA	NA	NA	2000.0	NA	NA	NA
us-gaap:MinorityInterest	▅▄▅███▇▇▇▇▇▇▆▆▆▁▁▁	246.522	244.647	247.378	283.822	281.298	285.365	277.348	274.86	271.371	268.658	271.354	270.161	260.946	260.613	259.523	206.017	206.002	206.818
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	█▁▁▁	7.489	5.662	5.642	5.642	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree	█▁▁▁	7.525	5.662	5.662	5.662	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour	█▁▁▁	7.561	5.662	5.662	5.662	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive	█▁▁▁	7.597	5.662	5.662	5.662	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	█▁▁▁	440.411	275.062	280.723	280.723	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:StockholdersEquity	██▆▆▆▆▃▃▂▂▂▁▁▁▁▁▁▁	5446.943	5458.245	5029.943	4968.142	4972.291	4992.15	4293.51	4264.649	3915.532	3914.524	3929.907	3804.758	3802.927	3686.859	3700.793	3689.863	3756.469	3759.323
us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	██▆▆▆▆▄▃▂▂▂▂▂▁▁▁▁▁	5693.465	5702.892	5277.321	5251.964	5253.589	5277.515	4570.858	4539.509	4186.903	4183.182	4201.261	4074.919	4063.873	3947.472	3960.316	3895.88	3962.471	3966.141
us-gaap:CommonStockValue	███▇▇▇▄▄▂▂▂▂▂▁▁▁▁▁	1.165	1.165	1.16	1.152	1.152	1.151	1.06	1.06	1.01	1.01	1.007	1.007	1.006	0.988	0.986	0.984	0.984	0.983
us-gaap:AdditionalPaidInCapital	██████▄▄▂▂▂▂▂▁▁▁▁▁	5134.32	5122.584	5131.916	5089.926	5084.362	5067.181	4350.917	4342.296	3984.867	3976.204	3976.953	3965.405	3951.289	3816.385	3822.492	3797.546	3792.028	3782.291
us-gaap:RetainedEarningsAccumulatedDeficit	██▂▂▂▂▂▂▂▂▃▁▁▁▂▂▁▂	311.458	334.496	-103.133	-122.936	-113.223	-76.182	-58.467	-78.707	-70.345	-62.69	-48.053	-161.654	-149.368	-130.514	-122.685	-108.667	-132.799	-120.207
us-gaap:MinorityInterest	▅▄▅███▇▇▇▇▇▇▆▆▆▁▁▁	246.522	244.647	247.378	283.822	281.298	285.365	277.348	274.86	271.371	268.658	271.354	270.161	260.946	260.613	259.523	206.017	206.002	206.818
us-gaap:StockIssuedDuringPeriodValueNewIssues		NA	NA	NA	-0.074	-0.045	721.794	NA	353.904	NA	NA	-0.051	6.597	124.147	NA	17.246	-0.02	-0.017	308.849
us-gaap:StockIssuedDuringPeriodValueNewIssues us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital		NA	NA	NA	-0.074	-0.045	721.705	NA	353.854	NA	NA	-0.051	6.596	124.13	NA	17.244	-0.02	-0.017	308.805
us-gaap:StockIssuedDuringPeriodValueNewIssues us-gaap:StatementEquityComponents us-gaap:Parent		NA	NA	NA	-0.074	-0.045	721.794	NA	353.904	NA	NA	-0.051	6.597	124.147	NA	17.246	-0.02	-0.017	308.849
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	█▁	11.193	9.604	NA	7.794	13.576	8.653	NA	6.808	8.732	8.817	11.212	8.081	11.503	5.094	7.306	6.385	6.459	6.169
us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	▁█	4.692	11.68	NA	1.458	4.281	2.617	NA	3.041	1.487	6.309	4.797	0.541	4.288	2.177	4.308	3.583	3.923	4.728

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities	▂█▃█▄▆▃▇▁▄▃▇▄▄▁▄▂▄	72.314	144.152	91.61	139.958	101.082	122.94	85.131	135.73	65.87	99.79	92.828	128.372	94.734	94.109	70.47	98.126	82.041	96.375
us-gaap:NetCashProvidedByUsedInInvestingActivities	▁█▄▄▄▃▂▃▃▃▄▄▂▃▃▄▄▄	-716.948	812.25	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35.306	-129.63	-86.388
us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity krc:KilroyRealtyL.P.	▁█▄▄▄▃▂▃▃▃▄▄▂▃▃▄	-716.948	812.25	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35.306	NA	NA
us-gaap:NetCashProvidedByUsedInFinancingActivities	▂▂▂▄▂█▄▆▄▃▃▃▅▄▂▁▃▄	-72.18	-92.954	-67.362	205.399	-95.275	790.562	188.388	419.623	140.356	-1.299	-4.796	48.382	319.705	139.817	-69.512	-285.067	-42.136	225.474
us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity krc:KilroyRealtyL.P.	▂▂▂▄▂█▄▆▄▃▃▃▅▄▂▁	-72.18	-92.954	-67.362	205.399	-95.275	790.562	188.388	419.623	140.356	-1.299	-4.796	48.382	319.705	139.817	-69.512	-285.067	NA	NA
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	▁█▄▅▃▇▃▅▄▄▅▄▄▄▃▄▄▅	-716.814	863.448	-42.179	243.997	-157.122	702.09	-227.576	245.205	2.722	-115.041	84.517	35.7	-2.252	-13.729	-177.432	-151.635	-89.725	235.461
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect dei:LegalEntity krc:KilroyRealtyL.P.	▁█▄▅▃▇▃▅▄▄▅▄▄▄▃▄	-716.814	863.448	-42.179	243.997	-157.122	702.09	-227.576	245.205	2.722	-115.041	84.517	35.7	-2.252	-13.729	-177.432	-151.635	NA	NA

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:DepreciationDepletionAndAmortization	▆▇▆▆█▆▅▅▄▃▃▂▂▂▁▂▂▁	72.037	74.431	71.512	70.422	75.981	72.438	68.078	67.985	67.011	64.971	63.64	61.609	62.956	61.677	59.987	61.141	61.0	59.734
us-gaap:NetCashProvidedByUsedInOperatingActivities	▂█▃█▄▆▃▇▁▄▃▇▄▄▁▄▂▄	72.314	144.152	91.61	139.958	101.082	122.94	85.131	135.73	65.87	99.79	92.828	128.372	94.734	94.109	70.47	98.126	82.041	96.375
us-gaap:NetIncomeLoss		NA	NA	78.642	49.028	19.618	39.817	72.5	43.846	42.194	36.903	160.22	34.4	27.549	36.246	28.529	71.11	31.448	33.525
us-gaap:NetIncomeLoss dei:LegalEntity krc:KilroyRealtyL.P.		NA	NA	79.654	49.728	19.838	40.389	73.74	44.589	42.901	37.508	163.309	34.993	28.015	36.893	29.013	72.402	31.971	34.054
us-gaap:ProfitLoss	▁█▂▁▁▁▂▁▁▁▃▁▁▁▁▂▁▁	42.88	507.411	83.452	54.071	24.352	45.418	77.922	48.298	47.215	41.794	166.89	38.31	31.755	40.971	32.54	75.488	35.306	37.281
us-gaap:ShareBasedCompensation	▆▅▃▃█▄▄▃▄▄▆▄▅▁▃▂▂▁	9.538	7.877	5.955	5.979	11.528	6.783	6.807	6.118	6.871	7.211	9.031	6.634	8.669	3.598	5.429	4.651	4.832	4.134

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities	▁█▄▄▄▃▂▃▃▃▄▄▂▃▃▄▄▄	-716.948	812.25	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35.306	-129.63	-86.388
us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity krc:KilroyRealtyL.P.	▁█▄▄▄▃▂▃▃▃▄▄▂▃▃▄	-716.948	812.25	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35.306	NA	NA

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities	▂▂▂▄▂█▄▆▄▃▃▃▅▄▂▁▃▄	-72.18	-92.954	-67.362	205.399	-95.275	790.562	188.388	419.623	140.356	-1.299	-4.796	48.382	319.705	139.817	-69.512	-285.067	-42.136	225.474
us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity krc:KilroyRealtyL.P.	▂▂▂▄▂█▄▆▄▃▃▃▅▄▂▁	-72.18	-92.954	-67.362	205.399	-95.275	790.562	188.388	419.623	140.356	-1.299	-4.796	48.382	319.705	139.817	-69.512	-285.067	NA	NA
us-gaap:PaymentsOfDividends us-gaap:SubsequentEventType us-gaap:SubsequentEvent		NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:PaymentsOfDividendsCommonStock	▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁█	58.8	58.594	58.592	56.799	56.788	52.399	52.44	49.954	46.862	46.996	46.772	46.708	42.898	43.033	42.704	42.701	37.649	217.643

		2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31

Common Stock Value

us-gaap:CommonStockValue

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	1.165	1.165	1.16	1.152	1.152	1.151	1.06	1.06	1.01	1.01	1.007	1.007	1.006	0.988	0.986	0.984	0.984	0.983	0.932	0.923	0.923	0.922	0.923	0.922	0.884	0.88	0.863	0.834	0.829	0.822	0.822	0.821	0.757	0.753	0.749	0.747	0.689	0.683	0.588	0.585	0.585	0.524	0.523	0.431
Percentage of CommonStockValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30	2017-06-30	2017-03-31	2016-09-30	2016-06-30	2016-03-31	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-09-30	2011-06-30	2011-03-31	2010-09-30	2010-06-30	2010-03-31
Value	116	116	115	115	107	105	101	101	101	100	99	98	98	98	92	92	92	92	88	87	85	84	84	76	77	74	77	71	68	63	58	57	52	52	50	43
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30	2017-06-30
Value	118	117	117	117	109	107	103	103	103	102	101	100	100
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding	101.0	101.0	101.7	101.7	101.9	101.9	102.0	102.0	102.0	102.1	102.1	102.1	102.1

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30	2017-06-30	2017-03-31	2016-09-30	2016-06-30	2016-03-31	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-09-30	2011-06-30	2011-03-31	2010-09-30	2010-06-30	2010-03-31
Value	116	116	115	115	106	104	100	100	100	99	98	98	98	97	92	92	92	92	88	86	83	82	82	76	75	74	77	71	68	63	58	57	52	52	50	43
Percentage of WeightedAverageNumberOfSharesOutstandingBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30	2017-06-30
Value	117	117	117	117	108	106	102	102	102	101	100	100	100
Percentage of WeightedAverageNumberOfSharesOutstandingBasic	101.0	101.0	101.7	101.7	101.9	101.9	102.0	102.0	102.0	102.1	102.1	102.1	102.1

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	0.3	4.27	0.67	0.42	0.17	0.37	0.68	0.41	0.41	0.36	1.59	0.34	0.27	0.36	0.28	0.67	0.3	0.27	0.29	0.54	0.32	1.85	0.27	1.1	0.61	0.45	0.32	0.18	0.33	1.17	0.23	0.07	0.08	-0.02	2.49	-0.04	-0.02	1.06	0.68	0.17	-0.01	0.01	0.02	-0.01	-0.04	0.11
Percentage of EarningsPerShareBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:EarningsPerShareBasic dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	0.3	4.27	0.67	0.42	0.16	0.37	0.68	0.41	0.41	0.36	1.58	0.34	0.27	0.36	0.28	0.67	0.3	0.26
Percentage of EarningsPerShareBasic	100.0	100.0	100.0	100.0	94.1	100.0	100.0	100.0	100.0	100.0	99.4	100.0	100.0	100.0	100.0	100.0	100.0	96.3

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	0.3	4.26	0.67	0.42	0.17	0.37	0.67	0.41	0.41	0.36	1.58	0.33	0.27	0.36	0.28	0.67	0.3	0.26	0.29	0.54	0.31	1.84	0.27	1.09	0.61	0.45	0.32	0.18	0.32	1.14	0.23	0.07	0.08	-0.02	2.45	-0.04	-0.02	1.06	0.68	0.17	-0.01	0.01	0.02	-0.01	-0.04	0.11
Percentage of EarningsPerShareDiluted	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:EarningsPerShareDiluted dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	0.3	4.26	0.67	0.42	0.16	0.36	0.67	0.41	0.41	0.36	1.57	0.33	0.27	0.36	0.28	0.67	0.3	0.26
Percentage of EarningsPerShareDiluted	100.0	100.0	100.0	100.0	94.1	97.3	100.0	100.0	100.0	100.0	99.4	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Allocated Share Based Compensation Expense

us-gaap:AllocatedShareBasedCompensationExpense

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	11	9.6	7.6	7.8	13	8.7	8.4	6.8	8.7	8.8	11	8.1	11	5.1	7.3	6.4	6.5	6.2	7.3	6.8	6.6	5.9	5.3	4.3	5.0	4.3	4.2	4.0	3.5	2.9	2.4	2.5	2.3	2.4	9.6	2.4	2.4	1.5	1.4	1.4	1.4
Percentage of AllocatedShareBasedCompensationExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	741.7	969.7	3.3	654.4	1274.6	322.8	3.8	212.2	303.9	4.4	5.9	4.3	6.1	2.8	4.1	3.5	3.6	3.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType

krc:A2021PerformanceBasedRSUs

Period End	2021-06-30	2021-03-31
Value	1.8	1.0
Percentage of AllocatedShareBasedCompensationExpense	16.1	10.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	119.2	101.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:A2021PerformanceBasedRSUs	0.0	0.0

krc:AcceleratedCompensationRelatedtoSeverancePackages

Period End	2021-06-30	2020-09-30	2020-06-30
Value	4.1	0.2	4.1
Percentage of AllocatedShareBasedCompensationExpense	36.6	2.6	30.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	271.5	16.8	384.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:AcceleratedCompensationRelatedtoSeverancePackages	0.0	0.0	0.0

krc:PerformanceBasedRSUs

Period End	2020-09-30
Value	1.2
Percentage of AllocatedShareBasedCompensationExpense	15.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	100.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:PerformanceBasedRSUs	0.0

General And Administrative Expense

us-gaap:GeneralAndAdministrativeExpense

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	24	21	23	18	38	19	22	22	19	23	33	19	21	15	16	14	14	14	16	13	13	13	12	10	12	12	12	11	11	10	9.91	10	9.855	9.669	9.443	8.727	9.251	8.767	7.793	6.355	7.44	6.56	6.867	7.273	6.728	7.095
Percentage of GeneralAndAdministrativeExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	1623.0	2220.7	10.1	1558.1	3617.3	705.4	10.2	704.6	693.6	11.6	17.7	10.3	11.6	8.5	9.5	8.0	7.9	8.3	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:GeneralAndAdministrativeExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	24	21	23	18	38	19	22	22	19	23	33	19	21	15	16	14	14
Percentage of GeneralAndAdministrativeExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	1623.0	2220.7	10.1	1558.1	3617.3	705.4	10.2	704.6	693.6	11.6	17.7	10.3	11.6	8.5	9.5	8.0	7.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	1623.0	2220.7	0.0	1558.1	3617.3	705.4	0.0	704.6	693.6	1282.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	35	497	78	49	19	39	72	43	42	36	160	34	27	36	28	71	31	33	42	53	32	174	29	106	58	44	19	13	16	11	5.531	2.683	9.68	2.388	3.911	-0.665	2.277	4.962	3.265	1.427	1.181	1.843	1.885	3.319	0.047	6.647
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2373.4	50265.8	34.3	4113.1	1838.6	1477.4	32.9	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	39.2	17.4	18.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	36	502	79	49	19	40	73	44	42	37	163	34	28	36	29	72	31
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest	101.0	101.0	101.3	101.4	101.1	101.4	101.7	101.7	101.7	101.6	101.9	101.7	101.7	101.8	101.7	101.8	101.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2396.9	50759.3	34.7	4171.8	1859.2	1498.7	33.5	1391.7	1498.5	18.6	85.6	18.8	15.0	20.2	16.3	39.9	17.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	2396.9	50759.3	0.0	4171.8	1859.2	1498.7	0.0	1391.7	1498.5	2060.9	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Interest Expense

us-gaap:InterestExpense

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	21	22	20	19	15	14	13	11	11	11	12	11	12	13	14	16	17	17	14	14	14	11	13	12	14	16	17	16	16	17	17	18	19	19	18	19	19	21	23	24	21	20	19	15	13	11
Percentage of InterestExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	1416.6	2256.0	9.1	1633.2	1488.7	536.0	6.3	363.1	409.6	5.6	6.5	5.9	6.8	7.4	8.2	8.9	10.0	9.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:InterestExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	21	22	20	19	15	14	13	11	11	11	12	11	12	13	14	16	17
Percentage of InterestExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	1416.6	2256.0	9.1	1633.2	1488.7	536.0	6.3	363.1	409.6	5.6	6.5	5.9	6.8	7.4	8.2	8.9	10.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	1416.6	2256.0	0.0	1633.2	1488.7	536.0	0.0	363.1	409.6	617.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Interest Paid Net

us-gaap:InterestPaidNet

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	29	12	25	10	15	10	15	5.13	18	4.706	12	7.039	15	9.699	20	15	12	18	11	17	11	13	9.069	13	12	19	16	11	17	14	18	15	20	11	22	12	32	4.487	26	7.502	27	6.965	19	7.548	11	6.98
Percentage of InterestPaidNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	1929.3	1251.2	11.3	872.8	1448.8	372.4	7.0	160.1	639.3	2.3	6.6	3.8	8.3	5.3	11.5	8.8	7.1	10.2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:InterestPaidNet dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	29	12	25	10	15	10	15	5.13	18	4.706	12	7.039	15	9.699	20	15
Percentage of InterestPaidNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	1929.3	1251.2	11.3	872.8	1448.8	372.4	7.0	160.1	639.3	2.3	6.6	3.8	8.3	5.3	11.5	8.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	1929.3	1251.2	0.0	872.8	1448.8	372.4	0.0	160.1	639.3	258.6	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss

us-gaap:NetIncomeLoss

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	78	49	19	39	72	43	42	36	160	34	27	36	28	71	31	33	32	53	32	174	28	104	57	43	30	18	30	99	22	8.896	9.946	2.41	189	2.589	2.297	76	43	13	3.482	4.833	5.334	3.673	2.016	8.685
Percentage of NetIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	34.3	4113.1	1838.6	1477.4	32.9	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	39.2	17.4	18.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetIncomeLoss dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	79	49	19	40	73	44	42	37	163	34	28	36	29	72	31	34
Percentage of NetIncomeLoss	101.3	101.4	101.1	101.4	101.7	101.7	101.7	101.6	101.9	101.7	101.7	101.8	101.7	101.8	101.7	101.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	34.7	4171.8	1859.2	1498.7	33.5	1391.7	1498.5	18.6	85.6	18.8	15.0	20.2	16.3	39.9	17.7	19.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	0.0	4171.8	1859.2	1498.7	0.0	1391.7	1498.5	2060.9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31
Value	7.041	9.78	4.81	5.043	4.734	5.601	5.422	4.452	5.021	4.891	6.67	3.91	4.206	4.725	4.011	4.378	3.858	3.756	2.68	2.48	1.045	3.805	0.673	1.945	1.09	0.815
Percentage of NetIncomeLossAttributableToNoncontrollingInterest	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	466.3	987.9	2.1	423.1	443.7	207.8	2.5	139.0	175.4	2.4	3.5	2.1	2.2	2.6	2.3	2.4	2.1	2.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	6.687	4.894	3.798	4.343	4.514	5.029	4.182	3.709	4.314	4.286	3.581	3.317	3.74	4.078	3.527	3.086	3.335
Percentage of NetIncomeLossAttributableToNoncontrollingInterest	95.0	50.0	79.0	86.1	95.4	89.8	77.1	83.3	85.9	87.6	53.7	84.8	88.9	86.3	87.9	70.5	86.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	442.8	494.3	1.7	364.3	423.1	186.6	1.9	115.8	150.7	2.1	1.9	1.8	2.0	2.2	2.0	1.7	1.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	442.8	494.3	0.0	364.3	423.1	186.6	0.0	115.8	150.7	235.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	35	497	78	49	19	39	72	43	42	36	160	34	27	36	28	66	29	26	29	50	29	170	25	101	54	39	27	15	27	96	19	5.584	6.633	-0.903	185	-2.753	-0.8	67	39	10	-0.317	1.034	1.535	-0.126	-1.783	4.886
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2373.4	50265.8	34.3	4113.1	1838.6	1477.4	32.9	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	36.7	16.5	14.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	36	502	79	49	19	40	73	44	42	37	163	34	28	36	29	67	30	26
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic	101.0	101.0	101.3	101.4	101.1	101.4	101.7	101.7	101.7	101.6	101.9	101.7	101.7	101.8	101.7	101.9	101.8	102.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2396.9	50759.3	34.7	4171.8	1859.2	1498.7	33.5	1391.7	1498.5	18.6	85.6	18.8	15.0	20.2	16.3	37.4	16.8	15.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	2396.9	50759.3	0.0	4171.8	1859.2	1498.7	0.0	1391.7	1498.5	2060.9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	-19.51	436	16	-17.599	-13.046	-17.572	17	-10.874	-3.942	-9.415	127	-10.733	-11.941	-13.464	-18.002	-14.625	-16.935	-16.287	-13.97	-14.438	-14.073	-11.558	-13.055	-13.513	-14.353	-16.518	-17.717	-16.617	-15.601	-17.075	-17.298	-18.18	-19.415	-19.342	-18.797	-19.524	-19.265	-20.679	-22.955	-24.021	-21.17	-20.692	-18.783	-15.516	-17.67	-11.572
Percentage of NonoperatingIncomeExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-1292.1	44073.4	7.2	-1476.4	-1222.7	-652.0	7.8	-339.4	-137.7	-4.7	67.1	-5.8	-6.4	-7.4	-10.1	-8.1	-9.4	-9.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NonoperatingIncomeExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	-19.51	436	16	-17.599	-13.046	-17.572	17	-10.874	-3.942	-9.415	127	-10.733	-11.941	-13.464	21	-14.625	-16.935
Percentage of NonoperatingIncomeExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	-122.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-1292.1	44073.4	7.2	-1476.4	-1222.7	-652.0	7.8	-339.4	-137.7	-4.7	67.1	-5.8	-6.4	-7.4	12.4	-8.1	-9.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	-1292.1	44073.4	0.0	-1476.4	-1222.7	-652.0	0.0	-339.4	-137.7	-517.3	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Operating Expenses

us-gaap:OperatingExpenses

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	163	164	162	156	182	158	159	156	149	149	151	137	143	128	127	129	128	127	119	115	111	101	104	99	104	102	104	99	100	97	97	94	95	95	88	85	82	73	71	71	67	62	60	60	52	46
Percentage of OperatingExpenses	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	10834.0	16622.4	70.8	13141.3	17059.5	5875.3	72.4	4879.9	5216.0	74.5	79.6	73.7	76.6	70.2	71.5	71.1	71.1	71.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:OperatingExpenses dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	163	164	162	156	182	158	159	156	149	149	151	137	143	128	127	129	128
Percentage of OperatingExpenses	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	10834.0	16622.4	70.8	13141.3	17059.5	5875.3	72.4	4879.9	5216.0	74.5	79.6	73.7	76.6	70.2	71.5	71.1	71.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	10834.0	16622.4	0.0	13141.3	17059.5	5875.3	0.0	4879.9	5216.0	8241.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Profit Loss

us-gaap:ProfitLoss

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	42	507	83	54	24	45	77	48	47	41	166	38	31	40	32	75	35	37	35	56	33	178	29	106	58	44	31	19	31	101	23	9.027	10	2.388	193	2.522	2.277	78	44	14	3.472	4.867	5.384	3.669	1.956	8.877
Percentage of ProfitLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2839.7	51253.6	36.4	4536.2	2282.3	1685.3	35.4	1507.4	1649.1	20.8	87.4	20.5	17.0	22.4	18.3	41.6	19.5	20.8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:ProfitLoss dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	42	507	83	54	24	45	77	48	47	41	166	38	31	40	32	75	35	37
Percentage of ProfitLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2839.7	51253.6	36.4	4536.2	2282.3	1685.3	35.4	1507.4	1649.1	20.8	87.4	20.5	17.0	22.4	18.3	41.6	19.5	20.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	2839.7	51253.6	0.0	4536.2	2282.3	1685.3	0.0	1507.4	1649.1	2296.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:ProfitLoss dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	36	502	49	19	40	44	42	37	163	34	28	36	29	72
Percentage of ProfitLoss	84.4	99.0	92.0	81.5	88.9	92.3	90.9	89.7	97.9	91.3	88.2	90.0	89.2	95.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2396.9	50759.3	4171.8	1859.2	1498.7	1391.7	1498.5	18.6	85.6	18.8	15.0	20.2	16.3	39.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P. krc:PartnersCapitalCommonUnit	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

krc:KilroyRealtyL.P., us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	6.687	4.894	4.343	4.514	5.029	3.709	4.314	4.286	3.581	3.317	3.74	4.078	3.527	3.086
Percentage of ProfitLoss	15.6	1.0	8.0	18.5	11.1	7.7	9.1	10.3	2.1	8.7	11.8	10.0	10.8	4.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	442.8	494.3	364.3	423.1	186.6	115.8	150.7	2.1	1.9	1.8	2.0	2.2	2.0	1.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P. us-gaap:NoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:ProfitLoss us-gaap:StatementEquityComponents

us-gaap:AccumulatedDistributionsInExcessOfNetIncome

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	35	497	49	19	39	43	42	36	160	34	27	36	28	71	31	33	32	53	32	174	28	104	57	43	30	18	30	99	22	8.896	9.946	2.41	189	2.59	2.297	76	43	13	3.482	4.833	5.334	3.673	2.016	8.685
Percentage of ProfitLoss	83.6	98.1	90.7	80.6	87.7	90.8	89.4	88.3	96.0	89.8	86.8	88.5	87.7	94.2	89.1	89.9	92.4	95.6	96.9	97.9	97.7	98.2	98.1	98.1	98.2	98.3	98.1	98.0	98.2	98.5	98.4	100.9	97.7	102.7	100.9	97.7	97.4	97.9	100.3	99.3	99.1	100.1	103.1	97.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2373.4	50265.8	4113.1	1838.6	1477.4	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	39.2	17.4	18.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:AccumulatedDistributionsInExcessOfNetIncome	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	7.041	9.78	5.043	4.734	5.601	4.452	5.021	4.891	6.67	3.91	4.206	4.725	4.011	4.378	3.858	3.756	2.68	2.48	1.045	3.805	0.673	1.945	1.09	0.815	0.578	0.321	0.603	2.087	0.419	0.131	0.157	-0.022	4.479	-0.067	-0.02	1.795	1.154	0.296	-0.01	0.034	0.05	-0.004	-0.06	0.192
Percentage of ProfitLoss	16.4	1.9	9.3	19.4	12.3	9.2	10.6	11.7	4.0	10.2	13.2	11.5	12.3	5.8	10.9	10.1	7.6	4.4	3.1	2.1	2.3	1.8	1.9	1.9	1.8	1.7	1.9	2.0	1.8	1.5	1.6	-0.9	2.3	-2.7	-0.9	2.3	2.6	2.1	-0.3	0.7	0.9	-0.1	-3.1	2.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	466.3	987.9	423.1	443.7	207.8	139.0	175.4	2.4	3.5	2.1	2.2	2.6	2.3	2.4	2.1	2.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:Parent

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	35	497	49	19	39	43	42	36	160	34	27	36	28	71	31	33	32	53	32	174	28	104	57	43	30	18	30	99	22	8.896	9.946	2.41	189	2.59	2.297	76	43	13	3.482	4.833	5.334	3.673	2.016	8.685
Percentage of ProfitLoss	83.6	98.1	90.7	80.6	87.7	90.8	89.4	88.3	96.0	89.8	86.8	88.5	87.7	94.2	89.1	89.9	92.4	95.6	96.9	97.9	97.7	98.2	98.1	98.1	98.2	98.3	98.1	98.0	98.2	98.5	98.4	100.9	97.7	102.7	100.9	97.7	97.4	97.9	100.3	99.3	99.1	100.1	103.1	97.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2373.4	50265.8	4113.1	1838.6	1477.4	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	39.2	17.4	18.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:Parent	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Revenue From Contract With Customer Excluding Assessed Tax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	1.51	0.99	229	1.192	1.067	2.695	220	3.204	2.863	201	190	186	187	182	177	181	180	179
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	1.51	0.99	1.137	1.192	1.067	2.695	3.095	3.204	2.863	1.82
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	100.0	100.0	0.5	100.0	100.0	100.0	1.4	100.0	100.0	0.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	100.0	100.0	0.5	100.0	100.0	100.0	1.4	100.0	100.0	0.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Revenues

us-gaap:Revenues

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	225	235	229	228	219	221	220	215	200	201	190	186	187	182	177	181	180	179
Percentage of Revenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	14965.8	23802.6	100.0	19153.9	20564.5	8212.5	100.0	6726.7	7002.9	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:Revenues dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	225	235	229	228	219	221	220	215	200	201	190	186	187	182	177	181	180	179
Percentage of Revenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	14965.8	23802.6	100.0	19153.9	20564.5	8212.5	100.0	6726.7	7002.9	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	14965.8	23802.6	20169.9	19153.9	20564.5	8212.5	7115.8	6726.7	7002.9	11055.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Assets

us-gaap:Assets

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	10434	10384	10000	9984	9658	9735	8900	8623	8094	7883	7765	7562	7384	6965	6802	6838	6995	6993	6706	6332	6298	6204	5939	6353	5686	5725	5633	5487	5273	5114	5111	5089	4775	4755	4616	4215	3847	3959	3446	3367	3264	2841	2816	2084
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:Assets dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	10434	10384	10000	9984	9658	9735	8900	8623	8094	7883	7765	7562	7384	6802
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets krc:KilroyRealtyL.P.	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:Assets us-gaap:ConsolidatedEntities

us-gaap:VariableInterestEntityPrimaryBeneficiary

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31
Value	461	454	469	477	686	686	676
Percentage of Assets	4.4	4.4	4.7	4.8	7.1	7.0	7.6
Percentage of Assets	4.4	4.4	4.7	4.8	7.1	7.0	7.6
Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:Assets us-gaap:ConsolidatedEntities, us-gaap:InvestmentType

us-gaap:VariableInterestEntityPrimaryBeneficiary, us-gaap:RealEstateInvestment

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31
Value	393	389	394	395	598	599	598
Percentage of Assets	3.8	3.8	3.9	4.0	6.2	6.2	6.7
Percentage of Assets	3.8	3.8	3.9	4.0	6.2	6.2	6.7
Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:RealEstateInvestment	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Liabilities

us-gaap:Liabilities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	4741	4681	4723	4732	4405	4457	4329	4084	3907	3700	3564	3487	3320	3018	2842	2942	3032	3027	2947	2690	2871	2779	2704	3116	2773	2866	2909	2867	2650	2528	2594	2565	2537	2522	2380	2154	2040	2155	2045	1999	1887	1665	1625	1126
Percentage of Liabilities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	45.4	45.1	47.2	47.4	45.6	45.8	48.6	47.4	48.3	46.9	45.9	46.1	45.0	43.3	41.8	43.0	43.4	43.3	43.9	42.5	45.6	44.8	45.5	49.0	48.8	50.1	51.6	52.2	50.3	49.4	50.8	50.4	53.1	53.1	51.6	51.1	53.0	54.4	59.4	59.4	57.8	58.6	57.7	54.1

us-gaap:Liabilities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	4741	4681	4723	4732	4405	4457	4329	4084	3907	3700	3564	3487	3320	2842
Percentage of Liabilities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	45.4	45.1	47.2	47.4	45.6	45.8	48.6	47.4	48.3	46.9	45.9	46.1	45.0	41.8
Percentage of Assets krc:KilroyRealtyL.P.	45.4	45.1	47.2	47.4	45.6	45.8	48.6	47.4	48.3	46.9	45.9	46.1	45.0	41.8

us-gaap:Liabilities us-gaap:ConsolidatedEntities

us-gaap:VariableInterestEntityPrimaryBeneficiary

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31
Value	28	34	33	35	42	43	40
Percentage of Liabilities	0.6	0.7	0.7	0.7	1.0	1.0	0.9
Percentage of Assets	0.3	0.3	0.3	0.4	0.4	0.5	0.5
Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary	6.1	7.6	7.2	7.4	6.2	6.4	5.9

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	10434	10384	10000	9984	9658	9735	8900	8623	8094	7883	7765	7562	7384	6965	6802	6838	6995	6993	6706	6332	6298	6204	5939	6353	5686	5725	5633	5487	5273	5114	5111	5089	4775	4755	4616	4215	3847	3959	3446	3367	3264	2841	2816	2084
Percentage of LiabilitiesAndStockholdersEquity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LiabilitiesAndStockholdersEquity dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	10434	10384	10000	9984	9658	9735	8900	8623	8094	7883	7765	7562	7384	6802
Percentage of LiabilitiesAndStockholdersEquity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets krc:KilroyRealtyL.P.	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Stockholders Equity

us-gaap:StockholdersEquity

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	5446	5458	5029	4968	4972	4992	4293	4264	3915	3914	3929	3804	3802	3686	3700	3689	3756	3759	3542	3463	3330	3328	3170	3172	2852	2800	2666	2563	2566	2529	2461	2468	2186	2185	2189	2019	1693	1690	1293	1261	1270	1071	1086	854
Percentage of StockholdersEquity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	52.2	52.6	50.3	49.8	51.5	51.3	48.2	49.5	48.4	49.7	50.6	50.3	51.5	52.9	54.4	54.0	53.7	53.8	52.8	54.7	52.9	53.6	53.4	49.9	50.2	48.9	47.3	46.7	48.7	49.5	48.2	48.5	45.8	45.9	47.4	47.9	44.0	42.7	37.5	37.5	38.9	37.7	38.6	41.0

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31	2009-12-31	2008-12-31	2007-12-31
Value	519	657	731	849	605	762	60	297	52	49	51	86	50	53	57	64	387	478	193	250	26	38	56	567	28	50	23	200	24	95	35	197	107	135	16	16	18	374	4.777	15	25	6.708	14	8.313	29	10	9.883	9.553	11
Percentage of CashAndCashEquivalentsAtCarryingValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	5.0	6.3	7.3	8.5	6.3	7.8	0.7	3.5	0.6	0.6	0.7	1.1	0.7	0.8	0.8	0.9	5.5	6.8	2.9	4.0	0.4	0.6	1.0	8.9	0.5	0.9	0.4	3.7	0.5	1.9	0.7	3.9	2.3	2.9	0.4	0.4	0.5	9.5	0.1	0.5	0.8	0.2	0.5	0.0	0.0	0.0	0.5	0.0	0.0

us-gaap:CashAndCashEquivalentsAtCarryingValue dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2015-12-31
Value	519	657	731	849	605	762	60	297	52	49	51	86	50	53	57	64	387	193	56
Percentage of CashAndCashEquivalentsAtCarryingValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	5.0	6.3	7.3	8.5	6.3	7.8	0.7	3.5	0.6	0.6	0.7	1.1	0.7	0.8	0.8	0.9	5.5	2.9	1.0
Percentage of Assets krc:KilroyRealtyL.P.	5.0	6.3	7.3	8.5	6.3	7.8	0.7	3.5	0.6	0.6	0.7	1.1	0.7	0.0	0.8	0.0	0.0	0.0	0.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2015-12-31	2014-12-31
Value	969	1686	823	865	621	778	76	303	58	55	171	86	50	53	66	244	395	485	250	57	98
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	9.3	16.2	8.2	8.7	6.4	8.0	0.9	3.5	0.7	0.7	2.2	1.1	0.7	0.8	1.0	3.6	5.7	6.9	3.7	1.0	1.8

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2015-12-31
Value	969	1686	823	865	621	778	76	303	58	55	171	86	50	53	66	244	395	250	57
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	9.3	16.2	8.2	8.7	6.4	8.0	0.9	3.5	0.7	0.7	2.2	1.1	0.7	0.8	1.0	3.6	5.7	3.7	1.0
Percentage of Assets krc:KilroyRealtyL.P.	9.3	16.2	8.2	8.7	6.4	8.0	0.9	3.5	0.7	0.7	2.2	1.1	0.7	0.0	1.0	0.0	0.0	0.0	0.0

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent

Period End	2020-12-31	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31
Value	12	26	20	17	15	17	16	18	13	13	13	9.709	10	9.54	11
Percentage of AccountsReceivableNetCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.1	0.3	0.3	0.2	0.2	0.3	0.2	0.3	0.2	0.2	0.2	0.2	0.2	0.2	0.2

Furniture And Fixtures Gross

us-gaap:FurnitureAndFixturesGross

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2015-12-31
Value	40	40	43	42	53	35	35	36	36	36	36	36	37	38	39	39	39	39	40	11
Percentage of FurnitureAndFixturesGross	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.4	0.4	0.4	0.4	0.5	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.6	0.2

Finite Lived Intangible Assets Net

us-gaap:FiniteLivedIntangibleAssetsNet krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsNet

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	196	185	166	146	150	144	147	146	133	126	123	126	141	125	113	115	115	110	109	108	106	97	95	89
Percentage of FiniteLivedIntangibleAssetsNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	2.0	2.1	2.1	2.2	2.2	2.3	2.3	2.4	2.2	2.0	2.2	2.2	2.5	2.3	2.1	2.3	2.3	2.2	2.3	2.3	2.3	2.3	2.5	2.6
Percentage of Assets krc:DeferredLeasingCosts	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	14	26	30	35	54	32	35	35	38	41	44	49	53	49	54	60	57	64	65	72	67	71	54	45
Percentage of FiniteLivedIntangibleAssetsNet	7.5	14.2	18.3	24.2	36.1	22.9	24.3	24.6	29.2	33.0	36.1	38.9	37.9	39.8	48.3	52.3	49.6	58.0	59.4	66.7	62.9	73.6	56.8	50.9
Percentage of Assets	0.1	0.3	0.4	0.5	0.8	0.5	0.6	0.6	0.7	0.7	0.8	0.9	0.9	0.9	1.0	1.2	1.1	1.3	1.4	1.5	1.5	1.7	1.4	1.3
Percentage of Assets us-gaap:LeasesAcquiredInPlace	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2019-01-01
Value	141	95	95	95	95	96	96	83	82	82	82
Percentage of OperatingLeaseRightOfUseAsset	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	1.4	0.9	1.0	1.0	1.0	1.0	1.1	1.0	1.0	1.1	0.0

us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2019-01-01
Value	141	95	95	95	95	96	96	83	82	82	82
Percentage of OperatingLeaseRightOfUseAsset	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	1.4	0.9	1.0	1.0	1.0	1.0	1.1	1.0	1.0	1.1	0.0
Percentage of Assets krc:KilroyRealtyL.P.	1.4	0.9	1.0	1.0	1.0	1.0	1.1	1.0	1.0	1.1	0.0

us-gaap:OperatingLeaseRightOfUseAsset us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

krc:A200West6thStreetAustinTX

Period End	2021-06-23
Value	46
Percentage of OperatingLeaseRightOfUseAsset	0.0
Percentage of Assets	0.0
Percentage of Assets krc:A200West6thStreetAustinTX	0.0

Long Term Debt

us-gaap:LongTermDebt dei:LegalEntity, us-gaap:LongtermDebtType

us-gaap:LongTermDebt

krc:KilroyRealtyL.P., us-gaap:SecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	253	258	335	340
Percentage of LongTermDebt	100.0	100.0	100.0	100.0
Percentage of Assets	2.5	2.9	4.3	5.0
Percentage of Assets krc:KilroyRealtyL.P. us-gaap:SecuredDebt	0.0	0.0	0.0	0.0

us-gaap:LongTermDebt us-gaap:LongtermDebtType

us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31
Value	3700	3300	2600	2000	1800	1900	1900	1600	1500
Percentage of LongTermDebt	1459.1	1276.1	774.9	586.9	0.0	0.0	0.0	0.0	0.0
Percentage of Assets	37.0	37.1	33.5	29.4	26.8	32.0	33.7	31.3	32.5
Percentage of Assets us-gaap:UnsecuredDebt	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Minority Interest

us-gaap:MinorityInterest

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	246	244	247	283	281	285	277	274	271	268	271	270	260	260	259	206	206	206	216	178	96	96	63	64	60	59	57	56	56	56	54	55	52	47	46	42	39	39	33	33	33	30	31	28
Percentage of MinorityInterest	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	2.4	2.4	2.5	2.8	2.9	2.9	3.1	3.2	3.4	3.4	3.5	3.6	3.5	3.7	3.8	3.0	2.9	3.0	3.2	2.8	1.5	1.6	1.1	1.0	1.1	1.0	1.0	1.0	1.1	1.1	1.1	1.1	1.1	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.1	1.1	1.4

Lessee Operating Lease Liability Payments Due Year Two

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	7489000.0	5662000.0	5642000.0	5642000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	100.0	100.0	100.0	100.0
Percentage of Assets	0.1	0.1	0.1	0.1

Lessee Operating Lease Liability Payments Due Year Three

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	7525000.0	5662000.0	5662000.0	5662000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearThree	100.0	100.0	100.0	100.0
Percentage of Assets	0.1	0.1	0.1	0.1

Lessee Operating Lease Liability Payments Due Year Four

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	7561000.0	5662000.0	5662000.0	5662000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFour	100.0	100.0	100.0	100.0
Percentage of Assets	0.1	0.1	0.1	0.1

Lessee Operating Lease Liability Payments Due Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	7597000.0	5662000.0	5662000.0	5662000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive	100.0	100.0	100.0	100.0
Percentage of Assets	0.1	0.1	0.1	0.1

Lessee Operating Lease Liability Payments Due After Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	440	275	280	280
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	100.0	100.0	100.0	100.0
Percentage of Assets	4.2	2.6	2.8	2.8

Operating Lease Liability

us-gaap:OperatingLeaseLiability

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2019-01-01
Value	143	97	97	97	98	98	98	87	87	87	87
Percentage of OperatingLeaseLiability	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	1.4	0.9	1.0	1.0	1.0	1.0	1.1	1.0	1.1	1.1	0.0

us-gaap:OperatingLeaseLiability dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2019-01-01
Value	143	97	97	97	98	98	98	87	87	87	87
Percentage of OperatingLeaseLiability	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	1.4	0.9	1.0	1.0	1.0	1.0	1.1	1.0	1.1	1.1	0.0
Percentage of Assets krc:KilroyRealtyL.P.	1.4	0.9	1.0	1.0	1.0	1.0	1.1	1.0	1.1	1.1	0.0

us-gaap:OperatingLeaseLiability us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

krc:A200West6thStreetAustinTX

Period End	2021-06-23
Value	46
Percentage of OperatingLeaseLiability	0.0
Percentage of Assets	0.0
Percentage of Assets krc:A200West6thStreetAustinTX	0.0

Lessee Operating Lease Liability Payments Due

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	481	307	308	310
Percentage of LesseeOperatingLeaseLiabilityPaymentsDue	100.0	100.0	100.0	100.0
Percentage of Assets	4.6	3.0	3.1	3.1

Lessee Operating Lease Liability Undiscounted Excess Amount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	337	209	211	212
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	100.0	100.0	100.0	100.0
Percentage of Assets	3.2	2.0	2.1	2.1

Stockholders Equity

us-gaap:StockholdersEquity

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	5446	5458	5029	4968	4972	4992	4293	4264	3915	3914	3929	3804	3802	3686	3700	3689	3756	3759	3542	3463	3330	3328	3170	3172	2852	2800	2666	2563	2566	2529	2461	2468	2186	2185	2189	2019	1693	1690	1293	1261	1270	1071	1086	854
Percentage of StockholdersEquity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	52.2	52.6	50.3	49.8	51.5	51.3	48.2	49.5	48.4	49.7	50.6	50.3	51.5	52.9	54.4	54.0	53.7	53.8	52.8	54.7	52.9	53.6	53.4	49.9	50.2	48.9	47.3	46.7	48.7	49.5	48.2	48.5	45.8	45.9	47.4	47.9	44.0	42.7	37.5	37.5	38.9	37.7	38.6	41.0

Stockholders Equity Including Portion Attributable To Noncontrolling Interest

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31	2009-12-31	2008-12-31	2007-12-31
Value	5693	5702	5277	5251	5253	5277	4570	4539	4186	4183	4201	4074	4063	3947	3960	3895	3962	3966	3759	3641	3426	3424	3234	3237	2913	2859	2723	2620	2623	2585	2516	2524	2238	2232	2235	2061	1733	1729	1327	1294	1303	1102	1117	1133	1152	874	883	714	767
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	54.6	54.9	52.8	52.6	54.4	54.2	51.4	52.6	51.7	53.1	54.1	53.9	55.0	56.7	58.2	57.0	56.6	56.7	56.1	57.5	54.4	55.2	54.5	51.0	51.2	49.9	48.4	47.8	49.7	50.6	49.2	49.6	46.9	46.9	48.4	48.9	45.0	43.7	38.5	38.4	39.9	38.8	39.7	0.0	0.0	0.0	42.4	0.0	0.0

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap:StatementEquityComponents

us-gaap:AccumulatedDistributionsInExcessOfNetIncome

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31	2009-12-31	2008-12-31	2007-12-31
Value	311	334	-103.133	-122.936	-113.223	-76.182	-58.467	-78.707	-70.345	-62.69	-48.053	-161.654	-149.368	-130.514	-122.685	-108.667	-132.799	-120.207	-107.997	78	62	67	-70.262	-62.85	-131.569	-154.355	-162.964	-159.799	-145.851	-143.636	-210.896	-201.048	-177.484	-157.211	-129.535	-288.765	-259.495	-234.199	-277.45	-296.476	-285.916	-264.848	-247.252	-230.215	-211.555	-191.19	-180.722	-137.052	-90.562
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	5.5	5.9	-2.0	-2.3	-2.2	-1.4	-1.3	-1.7	-1.7	-1.5	-1.1	-4.0	-3.7	-3.3	-3.1	-2.8	-3.4	-3.0	-2.9	2.1	1.8	2.0	-2.2	-1.9	-4.5	-5.4	-6.0	-6.1	-5.6	-5.6	-8.4	-8.0	-7.9	-7.0	-5.8	-14.0	-15.0	-13.5	-20.9	-22.9	-21.9	-24.0	-22.1	-20.3	-18.4	-21.9	-20.4	-19.2	-11.8
Percentage of Assets	3.0	3.2	-1.0	-1.2	-1.2	-0.8	-0.7	-0.9	-0.9	-0.8	-0.6	-2.1	-2.0	-1.9	-1.8	-1.6	-1.9	-1.7	-1.6	1.2	1.0	1.1	-1.2	-1.0	-2.3	-2.7	-2.9	-2.9	-2.8	-2.8	-4.1	-4.0	-3.7	-3.3	-2.8	-6.8	-6.7	-5.9	-8.0	-8.8	-8.8	-9.3	-8.8	0.0	0.0	0.0	-8.7	0.0	0.0
Percentage of Assets us-gaap:AccumulatedDistributionsInExcessOfNetIncome	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:AdditionalPaidInCapital

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31	2009-12-31	2008-12-31	2007-12-31
Value	5134	5122	5131	5089	5084	5067	4350	4342	3984	3976	3976	3965	3951	3816	3822	3797	3792	3782	3457	3191	3074	3066	3047	3042	2791	2761	2635	2530	2519	2479	2478	2476	2170	2149	2126	2114	1856	1827	1448	1435	1433	1214	1211	1209	1208	914	913	700	695
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	90.2	89.8	97.2	96.9	96.8	96.0	95.2	95.7	95.2	95.1	94.7	97.3	97.2	96.7	96.5	97.5	95.7	95.4	92.0	87.6	89.7	89.6	94.2	94.0	95.8	96.6	96.8	96.6	96.0	95.9	98.5	98.1	97.0	96.3	95.1	102.6	107.1	105.7	109.2	110.9	110.0	110.2	108.4	106.7	104.9	104.7	103.4	97.9	90.6
Percentage of Assets	49.2	49.3	51.3	51.0	52.6	52.1	48.9	50.4	49.2	50.4	51.2	52.4	53.5	54.8	56.2	55.5	54.2	54.1	51.6	50.4	48.8	49.4	51.3	47.9	49.1	48.2	46.8	46.1	47.8	48.5	48.5	48.7	45.5	45.2	46.1	50.2	48.3	46.2	42.0	42.6	43.9	42.7	43.0	0.0	0.0	0.0	43.8	0.0	0.0
Percentage of Assets us-gaap:AdditionalPaidInCapital	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:CommonStock

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31	2009-12-31	2008-12-31	2007-12-31
Value	1.165	1.165	1.16	1.152	1.152	1.151	1.06	1.06	1.01	1.01	1.007	1.007	1.006	0.988	0.986	0.984	0.984	0.983	0.932	0.923	0.923	0.922	0.923	0.922	0.884	0.88	0.863	0.834	0.829	0.822	0.822	0.821	0.757	0.753	0.749	0.747	0.689	0.683	0.588	0.585	0.585	0.524	0.523	0.523	0.523	0.431	0.431	0.331	0.328
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:CommonStock	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31	2009-12-31	2008-12-31	2007-12-31
Value	246	244	247	283	281	285	277	274	271	268	271	270	260	260	259	206	206	206	216	178	96	96	63	64	60	59	57	56	56	56	54	55	52	47	46	42	39	39	33	33	33	30	31	31	32	28	28	29	40
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	4.3	4.3	4.7	5.4	5.4	5.4	6.1	6.1	6.5	6.4	6.5	6.6	6.4	6.6	6.6	5.3	5.2	5.2	5.8	4.9	2.8	2.8	2.0	2.0	2.1	2.1	2.1	2.2	2.2	2.2	2.2	2.2	2.3	2.1	2.1	2.0	2.3	2.3	2.5	2.6	2.6	2.8	2.8	2.8	2.8	3.3	3.3	4.2	5.3
Percentage of Assets	2.4	2.4	2.5	2.8	2.9	2.9	3.1	3.2	3.4	3.4	3.5	3.6	3.5	3.7	3.8	3.0	2.9	3.0	3.2	2.8	1.5	1.6	1.1	1.0	1.1	1.0	1.0	1.0	1.1	1.1	1.1	1.1	1.1	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.1	1.1	0.0	0.0	0.0	1.4	0.0	0.0
Percentage of Assets us-gaap:NoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:Parent

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31	2009-12-31	2008-12-31	2007-12-31
Value	5446	5458	5029	4968	4972	4992	4293	4264	3915	3914	3929	3804	3802	3686	3700	3689	3756	3759	3542	3463	3330	3328	3170	3172	2852	2800	2666	2563	2566	2529	2461	2468	2186	2185	2189	2019	1693	1690	1293	1261	1270	1071	1086	1101	1119	845	854	684	726
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	95.7	95.7	95.3	94.6	94.6	94.6	93.9	93.9	93.5	93.6	93.5	93.4	93.6	93.4	93.4	94.7	94.8	94.8	94.2	95.1	97.2	97.2	98.0	98.0	97.9	97.9	97.9	97.8	97.8	97.8	97.8	97.8	97.7	97.9	97.9	98.0	97.7	97.7	97.5	97.4	97.4	97.2	97.2	97.2	97.2	96.7	96.7	95.8	94.7
Percentage of Assets	52.2	52.6	50.3	49.8	51.5	51.3	48.2	49.5	48.4	49.7	50.6	50.3	51.5	52.9	54.4	54.0	53.7	53.8	52.8	54.7	52.9	53.6	53.4	49.9	50.2	48.9	47.3	46.7	48.7	49.5	48.2	48.5	45.8	45.9	47.4	47.9	44.0	42.7	37.5	37.5	38.9	37.7	38.6	0.0	0.0	0.0	41.0	0.0	0.0
Percentage of Assets us-gaap:Parent	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Common Stock Value

us-gaap:CommonStockValue

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	1.165	1.165	1.16	1.152	1.152	1.151	1.06	1.06	1.01	1.01	1.007	1.007	1.006	0.988	0.986	0.984	0.984	0.983	0.932	0.923	0.923	0.922	0.923	0.922	0.884	0.88	0.863	0.834	0.829	0.822	0.822	0.821	0.757	0.753	0.749	0.747	0.689	0.683	0.588	0.585	0.585	0.524	0.523	0.431
Percentage of CommonStockValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Additional Paid In Capital

us-gaap:AdditionalPaidInCapital

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	5134	5122	5131	5089	5084	5067	4350	4342	3984	3976	3976	3965	3951	3816	3822	3797	3792	3782	3457	3191	3074	3066	3047	3042	2791	2761	2635	2530	2519	2479	2478	2476	2170	2149	2126	2114	1856	1827	1448	1435	1433	1214	1211	913
Percentage of AdditionalPaidInCapital	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	49.2	49.3	51.3	51.0	52.6	52.1	48.9	50.4	49.2	50.4	51.2	52.4	53.5	54.8	56.2	55.5	54.2	54.1	51.6	50.4	48.8	49.4	51.3	47.9	49.1	48.2	46.8	46.1	47.8	48.5	48.5	48.7	45.5	45.2	46.1	50.2	48.3	46.2	42.0	42.6	43.9	42.7	43.0	43.8

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31
Value	311	334	-103.133	-122.936	-113.223	-76.182	-58.467	-78.707	-70.345	-62.69	-48.053	-161.654	-149.368	-130.514	-122.685	-108.667	-132.799	-120.207	-107.997	78	62	67	-70.262
Percentage of RetainedEarningsAccumulatedDeficit	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	3.0	3.2	-1.0	-1.2	-1.2	-0.8	-0.7	-0.9	-0.9	-0.8	-0.6	-2.1	-2.0	-1.9	-1.8	-1.6	-1.9	-1.7	-1.6	1.2	1.0	1.1	-1.2

Minority Interest

us-gaap:MinorityInterest

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	246	244	247	283	281	285	277	274	271	268	271	270	260	260	259	206	206	206	216	178	96	96	63	64	60	59	57	56	56	56	54	55	52	47	46	42	39	39	33	33	33	30	31	28
Percentage of MinorityInterest	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	2.4	2.4	2.5	2.8	2.9	2.9	3.1	3.2	3.4	3.4	3.5	3.6	3.5	3.7	3.8	3.0	2.9	3.0	3.2	2.8	1.5	1.6	1.1	1.0	1.1	1.0	1.0	1.0	1.1	1.1	1.1	1.1	1.1	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.1	1.1	1.4

Stock Issued During Period Value New Issues

us-gaap:StockIssuedDuringPeriodValueNewIssues

Period End	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2010-12-31	2010-09-30
Value	-0.074	-0.045	721	353	-0.051	6.597	124	17	-0.02	-0.017	308	-0.111	249	24	113	101	0.0	0.0	307	19	23	9.731	253	26	382	12	0.0	0.0	0.0
Percentage of StockIssuedDuringPeriodValueNewIssues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:StockIssuedDuringPeriodValueNewIssues us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital

Period End	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2010-12-31	2010-09-30
Value	-0.074	-0.045	721	353	-0.051	6.596	124	17	-0.02	-0.017	308	-0.111	249	24	113	101	0.0	0.0	307	19	23	9.729	253	26	381	12	0.0	0.0	0.0
Percentage of StockIssuedDuringPeriodValueNewIssues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:AdditionalPaidInCapital	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:Parent

Period End	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2010-12-31	2010-09-30
Value	-0.074	-0.045	721	353	-0.051	6.597	124	17	-0.02	-0.017	308	-0.111	249	24	113	101	0.0	0.0	307	19	23	9.731	253	26	382	12	0.0	0.0	0.0
Percentage of StockIssuedDuringPeriodValueNewIssues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:Parent	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	11	9.604	7.794	13	8.653	6.808	8.732	8.817	11	8.081	11	5.094	7.306	6.385	6.459	6.169	7.321	6.765	6.627	5.911	5.248	4.37	4.949	4.302	4.126	3.961	4.151	2.233	2.467	2.385	2.289	2.422	2.355	2.355	2.358	1.469	1.387	1.388	1.393	1.42	1.637	1.689	1.641	1.72
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	11	9.604	7.794	13	8.653	6.808	8.732	8.817	11	8.081	11	5.094	7.306	6.385
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets krc:KilroyRealtyL.P.	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	11	9.604	7.794	13	8.653	6.808	8.732	8.817	11	8.081	11	5.094	7.306	6.385
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets krc:KilroyRealtyL.P. krc:PartnersCapitalCommonUnit	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	11	9.604	7.794	13	8.653	6.808	8.732	8.817	11	8.081	11	5.094	7.306	6.385	6.459	6.169	7.321	6.765	6.627	5.911	5.248	4.37	4.949	4.302	4.126	3.961	4.151	2.233	2.467	2.385	2.289	2.422	2.355	2.355	2.358	1.469	1.387	1.388	1.393	1.42	1.637	1.689	1.641	1.72
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:AdditionalPaidInCapital	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:Parent

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	11	9.604	7.794	13	8.653	6.808	8.732	8.817	11	8.081	11	5.094	7.306	6.385	6.459	6.169	7.321	6.765	6.627	5.911	5.248	4.37	4.949	4.302	4.126	3.961	4.151	2.233	2.467	2.385	2.289	2.422	2.355	2.355	2.358	1.469	1.387	1.388	1.393	1.42	1.637	1.689	1.641	1.72
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:Parent	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Minority Interest Decrease From Distributions To Noncontrolling Interest Holders

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30
Value	4.692	11	1.458	4.281	2.617	3.041	1.487	6.309	4.797	0.541	4.288	2.177	4.308	3.583	3.923	4.728	2.476	0.858
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	4.692	11	1.458	4.281	2.617	3.041	1.487	6.309	4.797	0.541	4.288	2.177	4.308	3.583
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets krc:KilroyRealtyL.P.	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	4.692	11	1.458	4.281	2.617	-3.041	1.487	6.309	4.797	0.541	4.288	2.177	4.308	3.583
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	100.0	100.0	100.0	100.0	100.0	-100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets krc:KilroyRealtyL.P. us-gaap:NoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30
Value	4.692	11	1.458	4.281	2.617	3.041	1.487	6.309	4.797	0.541	4.288	2.177	4.308	3.583	3.923	4.728	2.476	0.858
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:NoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	72	144	91	139	101	122	85	135	65	99	92	128	94	94	70	98	82	96	92	114	59	78	69	85	61	54	47	90	61	45	54	79	50	56	33	68	29	48	24	57	12	43	24	37	23	33
Percentage of NetCashProvidedByUsedInOperatingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	4789.0	14560.8	39.9	11741.4	9473.5	4561.8	38.7	4236.3	2300.7	49.6	48.6	68.8	50.6	51.5	39.7	54.1	45.4	53.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetCashProvidedByUsedInOperatingActivities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	72	144	91	139	101	122	85	135	65	99	92	128	94	94	70	98
Percentage of NetCashProvidedByUsedInOperatingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	4789.0	14560.8	39.9	11741.4	9473.5	4561.8	38.7	4236.3	2300.7	49.6	48.6	68.8	50.6	51.5	39.7	54.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	4789.0	14560.8	8057.2	11741.4	9473.5	4561.8	2750.6	4236.3	2300.7	5483.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	-716.948	812	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35	-129.63	-86.388	-511.228	180	-177.798	-126.733	-126.086	-51.646	-7.711	-77.309	-312.478	-67.094	-219.142	97	-224.856	-261.042	-64.069	43	-165.183	-239.731	-204.508	-97.084	-81.068	-117.696	-374.382	-61.137	-267.119	-20.547	-376.644	-37.464
Percentage of NetCashProvidedByUsedInInvestingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-47480.0	82045.5	-29.0	-8503.4	-15269.8	-7844.6	-227.5	-9680.0	-7108.1	-106.1	-1.8	-75.6	-222.7	-135.5	-100.5	19.4	-71.8	-48.2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-716.948	812	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35
Percentage of NetCashProvidedByUsedInInvestingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-47480.0	82045.5	-29.0	-8503.4	-15269.8	-7844.6	-227.5	-9680.0	-7108.1	-106.1	-1.8	-75.6	-222.7	-135.5	-100.5	19.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	-47480.0	82045.5	-5842.3	-8503.4	-15269.8	-7844.6	-16190.5	-9680.0	-7108.1	-11732.5	0.0	0.0	0.0	0.0	0.0	0.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	-72.18	-92.954	-67.362	205	-95.275	790	188	419	140	-1.299	-4.796	48	319	139	-69.512	-285.067	-42.136	225	361	-71.109	106	30	-454.742	505	-76.177	48	87	152	86	-82.202	8.817	271	-14.289	19	132	169	-181.64	417	46	50	380	9.208	248	-38.108	371	4.749
Percentage of NetCashProvidedByUsedInFinancingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-4780.1	-9389.3	-29.4	17231.5	-8929.2	29334.4	85.5	13096.8	4902.4	-0.6	-2.5	25.9	170.9	76.5	-39.1	-157.0	-23.3	125.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-72.18	-92.954	-67.362	205	-95.275	790	188	419	140	-1.299	-4.796	48	319	139	-69.512	-285.067
Percentage of NetCashProvidedByUsedInFinancingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-4780.1	-9389.3	-29.4	17231.5	-8929.2	29334.4	85.5	13096.8	4902.4	-0.6	-2.5	25.9	170.9	76.5	-39.1	-157.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	-4780.1	-9389.3	-5924.5	17231.5	-8929.2	29334.4	6086.8	13096.8	4902.4	-71.4	0.0	0.0	0.0	0.0	0.0	0.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	-716.814	863	-42.179	243	-157.122	702	-227.576	245	2.722	-115.041	84	35	-2.252	-13.729	-177.432	-151.635	-89.725	235
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-47471.1	87217.0	-18.4	20469.5	-14725.6	26051.6	-103.3	7653.1	95.1	-57.2	44.3	19.1	-1.2	-7.5	-99.9	-83.5	-49.7	131.3

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-716.814	863	-42.179	243	-157.122	702	-227.576	245	2.722	-115.041	84	35	-2.252	-13.729	-177.432	-151.635
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-47471.1	87217.0	-18.4	20469.5	-14725.6	26051.6	-103.3	7653.1	95.1	-57.2	44.3	19.1	-1.2	-7.5	-99.9	-83.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	-47471.1	87217.0	-3709.7	20469.5	-14725.6	26051.6	-7353.0	7653.1	95.1	-6320.9	0.0	0.0	0.0	0.0	0.0	0.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	72	74	71	70	75	72	68	67	67	64	63	61	62	61	59	61	61	59	55	55	52	49	50	48	50	50	53	49	50	48	50	50	48	50	45	45	40	36	38	35	31	29	28	29	23	20
Percentage of DepreciationDepletionAndAmortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DepreciationDepletionAndAmortization dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	72	74	71	70	75	72	68	67	67	64	63	61	62	61	59	61
Percentage of DepreciationDepletionAndAmortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	72	144	91	139	101	122	85	135	65	99	92	128	94	94	70	98	82	96	92	114	59	78	69	85	61	54	47	90	61	45	54	79	50	56	33	68	29	48	24	57	12	43	24	37	23	33
Percentage of NetCashProvidedByUsedInOperatingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	4789.0	14560.8	39.9	11741.4	9473.5	4561.8	38.7	4236.3	2300.7	49.6	48.6	68.8	50.6	51.5	39.7	54.1	45.4	53.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetCashProvidedByUsedInOperatingActivities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	72	144	91	139	101	122	85	135	65	99	92	128	94	94	70	98
Percentage of NetCashProvidedByUsedInOperatingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	4789.0	14560.8	39.9	11741.4	9473.5	4561.8	38.7	4236.3	2300.7	49.6	48.6	68.8	50.6	51.5	39.7	54.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	4789.0	14560.8	8057.2	11741.4	9473.5	4561.8	2750.6	4236.3	2300.7	5483.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss

us-gaap:NetIncomeLoss

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	78	49	19	39	72	43	42	36	160	34	27	36	28	71	31	33	32	53	32	174	28	104	57	43	30	18	30	99	22	8.896	9.946	2.41	189	2.589	2.297	76	43	13	3.482	4.833	5.334	3.673	2.016	8.685
Percentage of NetIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	34.3	4113.1	1838.6	1477.4	32.9	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	39.2	17.4	18.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetIncomeLoss dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	79	49	19	40	73	44	42	37	163	34	28	36	29	72	31	34
Percentage of NetIncomeLoss	101.3	101.4	101.1	101.4	101.7	101.7	101.7	101.6	101.9	101.7	101.7	101.8	101.7	101.8	101.7	101.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	34.7	4171.8	1859.2	1498.7	33.5	1391.7	1498.5	18.6	85.6	18.8	15.0	20.2	16.3	39.9	17.7	19.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	7005.6	4171.8	1859.2	1498.7	2382.6	1391.7	1498.5	2060.9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Profit Loss

us-gaap:ProfitLoss

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	42	507	83	54	24	45	77	48	47	41	166	38	31	40	32	75	35	37	35	56	33	178	29	106	58	44	31	19	31	101	23	9.027	10	2.388	193	2.522	2.277	78	44	14	3.472	4.867	5.384	3.669	1.956	8.877
Percentage of ProfitLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2839.7	51253.6	36.4	4536.2	2282.3	1685.3	35.4	1507.4	1649.1	20.8	87.4	20.5	17.0	22.4	18.3	41.6	19.5	20.8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:ProfitLoss dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	42	507	83	54	24	45	77	48	47	41	166	38	31	40	32	75	35	37
Percentage of ProfitLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2839.7	51253.6	36.4	4536.2	2282.3	1685.3	35.4	1507.4	1649.1	20.8	87.4	20.5	17.0	22.4	18.3	41.6	19.5	20.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	2839.7	51253.6	7339.7	4536.2	2282.3	1685.3	2517.7	1507.4	1649.1	2296.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:ProfitLoss dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	36	502	49	19	40	44	42	37	163	34	28	36	29	72
Percentage of ProfitLoss	84.4	99.0	92.0	81.5	88.9	92.3	90.9	89.7	97.9	91.3	88.2	90.0	89.2	95.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2396.9	50759.3	4171.8	1859.2	1498.7	1391.7	1498.5	18.6	85.6	18.8	15.0	20.2	16.3	39.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P. krc:PartnersCapitalCommonUnit	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

krc:KilroyRealtyL.P., us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	6.687	4.894	4.343	4.514	5.029	3.709	4.314	4.286	3.581	3.317	3.74	4.078	3.527	3.086
Percentage of ProfitLoss	15.6	1.0	8.0	18.5	11.1	7.7	9.1	10.3	2.1	8.7	11.8	10.0	10.8	4.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	442.8	494.3	364.3	423.1	186.6	115.8	150.7	2.1	1.9	1.8	2.0	2.2	2.0	1.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P. us-gaap:NoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:ProfitLoss us-gaap:StatementEquityComponents

us-gaap:AccumulatedDistributionsInExcessOfNetIncome

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	35	497	49	19	39	43	42	36	160	34	27	36	28	71	31	33	32	53	32	174	28	104	57	43	30	18	30	99	22	8.896	9.946	2.41	189	2.59	2.297	76	43	13	3.482	4.833	5.334	3.673	2.016	8.685
Percentage of ProfitLoss	83.6	98.1	90.7	80.6	87.7	90.8	89.4	88.3	96.0	89.8	86.8	88.5	87.7	94.2	89.1	89.9	92.4	95.6	96.9	97.9	97.7	98.2	98.1	98.1	98.2	98.3	98.1	98.0	98.2	98.5	98.4	100.9	97.7	102.7	100.9	97.7	97.4	97.9	100.3	99.3	99.1	100.1	103.1	97.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2373.4	50265.8	4113.1	1838.6	1477.4	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	39.2	17.4	18.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:AccumulatedDistributionsInExcessOfNetIncome	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	7.041	9.78	5.043	4.734	5.601	4.452	5.021	4.891	6.67	3.91	4.206	4.725	4.011	4.378	3.858	3.756	2.68	2.48	1.045	3.805	0.673	1.945	1.09	0.815	0.578	0.321	0.603	2.087	0.419	0.131	0.157	-0.022	4.479	-0.067	-0.02	1.795	1.154	0.296	-0.01	0.034	0.05	-0.004	-0.06	0.192
Percentage of ProfitLoss	16.4	1.9	9.3	19.4	12.3	9.2	10.6	11.7	4.0	10.2	13.2	11.5	12.3	5.8	10.9	10.1	7.6	4.4	3.1	2.1	2.3	1.8	1.9	1.9	1.8	1.7	1.9	2.0	1.8	1.5	1.6	-0.9	2.3	-2.7	-0.9	2.3	2.6	2.1	-0.3	0.7	0.9	-0.1	-3.1	2.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	466.3	987.9	423.1	443.7	207.8	139.0	175.4	2.4	3.5	2.1	2.2	2.6	2.3	2.4	2.1	2.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:Parent

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	35	497	49	19	39	43	42	36	160	34	27	36	28	71	31	33	32	53	32	174	28	104	57	43	30	18	30	99	22	8.896	9.946	2.41	189	2.59	2.297	76	43	13	3.482	4.833	5.334	3.673	2.016	8.685
Percentage of ProfitLoss	83.6	98.1	90.7	80.6	87.7	90.8	89.4	88.3	96.0	89.8	86.8	88.5	87.7	94.2	89.1	89.9	92.4	95.6	96.9	97.9	97.7	98.2	98.1	98.1	98.2	98.3	98.1	98.0	98.2	98.5	98.4	100.9	97.7	102.7	100.9	97.7	97.4	97.9	100.3	99.3	99.1	100.1	103.1	97.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	2373.4	50265.8	4113.1	1838.6	1477.4	1368.5	1473.8	18.3	84.0	18.4	14.7	19.8	16.1	39.2	17.4	18.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:Parent	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Share Based Compensation

us-gaap:ShareBasedCompensation

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	9.538	7.877	5.955	5.979	11	6.783	6.807	6.118	6.871	7.211	9.031	6.634	8.669	3.598	5.429	4.651	4.832	4.134	5.801	5.229	5.331	4.703	4.265	3.622	4.079	3.571	3.278	3.372	2.943	2.502	2.162	2.174	2.046	2.234	2.126	2.125	2.132	1.287	1.117	1.126	1.133	1.106	0.703	1.809	1.813	1.706
Percentage of ShareBasedCompensation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ShareBasedCompensation dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	9.538	7.877	5.955	5.979	11	6.783	6.807	6.118	6.871	7.211	9.031	6.634	8.669	3.598	5.429	4.651
Percentage of ShareBasedCompensation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	-716.948	812	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35	-129.63	-86.388	-511.228	180	-177.798	-126.733	-126.086	-51.646	-7.711	-77.309	-312.478	-67.094	-219.142	97	-224.856	-261.042	-64.069	43	-165.183	-239.731	-204.508	-97.084	-81.068	-117.696	-374.382	-61.137	-267.119	-20.547	-376.644	-37.464
Percentage of NetCashProvidedByUsedInInvestingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-47480.0	82045.5	-29.0	-8503.4	-15269.8	-7844.6	-227.5	-9680.0	-7108.1	-106.1	-1.8	-75.6	-222.7	-135.5	-100.5	19.4	-71.8	-48.2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-716.948	812	-66.427	-101.36	-162.929	-211.412	-501.095	-310.148	-203.504	-213.532	-3.515	-141.054	-416.691	-247.655	-178.39	35
Percentage of NetCashProvidedByUsedInInvestingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-47480.0	82045.5	-29.0	-8503.4	-15269.8	-7844.6	-227.5	-9680.0	-7108.1	-106.1	-1.8	-75.6	-222.7	-135.5	-100.5	19.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	-47480.0	82045.5	-5842.3	-8503.4	-15269.8	-7844.6	-16190.5	-9680.0	-7108.1	-11732.5	0.0	0.0	0.0	0.0	0.0	0.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	-72.18	-92.954	-67.362	205	-95.275	790	188	419	140	-1.299	-4.796	48	319	139	-69.512	-285.067	-42.136	225	361	-71.109	106	30	-454.742	505	-76.177	48	87	152	86	-82.202	8.817	271	-14.289	19	132	169	-181.64	417	46	50	380	9.208	248	-38.108	371	4.749
Percentage of NetCashProvidedByUsedInFinancingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-4780.1	-9389.3	-29.4	17231.5	-8929.2	29334.4	85.5	13096.8	4902.4	-0.6	-2.5	25.9	170.9	76.5	-39.1	-157.0	-23.3	125.7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-72.18	-92.954	-67.362	205	-95.275	790	188	419	140	-1.299	-4.796	48	319	139	-69.512	-285.067
Percentage of NetCashProvidedByUsedInFinancingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	-4780.1	-9389.3	-29.4	17231.5	-8929.2	29334.4	85.5	13096.8	4902.4	-0.6	-2.5	25.9	170.9	76.5	-39.1	-157.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax krc:KilroyRealtyL.P.	-4780.1	-9389.3	-5924.5	17231.5	-8929.2	29334.4	6086.8	13096.8	4902.4	-71.4	0.0	0.0	0.0	0.0	0.0	0.0

Payments Of Dividends

us-gaap:PaymentsOfDividends us-gaap:SubsequentEventType

us-gaap:PaymentsOfDividends

us-gaap:SubsequentEvent

Period End	2021-07-14	2021-04-14	2021-01-15	2020-10-14
Value	59	59	59	59
Percentage of PaymentsOfDividends	100.0	100.0	100.0	100.0

Payments Of Dividends Common Stock

us-gaap:PaymentsOfDividendsCommonStock

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-01-13	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	58	58	58	56	56	52	52	49	46	46	46	46	42	43	42	42	37	36	217	35	35	32	32	32	31	31	30	29	29	29	29	29	28	27	26	26	24	24	21	21	21	18	18	18	18	15	15
Percentage of PaymentsOfDividendsCommonStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsOfDividendsCommonStock dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	58	58	58	56	56	52	52	49	46	46	46	46	42	43	42	42
Percentage of PaymentsOfDividendsCommonStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:AnnualGroundLeaseRentalObligationsMaximum

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	0	1000000.0	0	0	0	1000000.0	0	0	0	1000000.0
Percentage of AnnualGroundLeaseRentalObligationsMaximum	0.0	100.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0	100.0

krc:AverageOccupancyPercentage us-gaap:PropertyPlantAndEquipmentByType

krc:AverageOccupancyPercentage

krc:StabilizedResidentialProperties

Period End	2021-06-30	2021-03-31
Value	1.5	69.1
Percentage of AverageOccupancyPercentage	100.0	100.0

krc:CommonStockholdersAndUnitholdersDividendsAndDistributionsDeclaredButNotPaid

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	-0.017	59	0.015	1.816	-0.02	57	0.014	2.405	3.124	47	0.148	0.063	3.836	43	0.124	0.019	5.129	38	184	0.016	2.416	33	-0.017	1.323	0.138	31	0.985	0.168	0.184	29	0.014	2.241	0.126	27	0.081	2.056	0.202	24	0.124	0.0	2.114	18	0.0	0.018	3.221	15
Percentage of CommonStockholdersAndUnitholdersDividendsAndDistributionsDeclaredButNotPaid	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	100.0	0.0	100.0	100.0	100.0

krc:CommonStockholdersAndUnitholdersDividendsAndDistributionsDeclaredButNotPaid dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-0.017	59	0.015	1.816	-0.02	57	0.014	2.405	3.124	47	0.148	0.063	3.836	43	0.124	0.019
Percentage of CommonStockholdersAndUnitholdersDividendsAndDistributionsDeclaredButNotPaid	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DepreciationNonRealEstateAssets

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	1552000.0	1501000.0	1478000.0	1441000.0	4104000.0	1932000.0	1435000.0	1245000.0	1241000.0	1164000.0
Percentage of DepreciationNonRealEstateAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DepreciationNonRealEstateAssets dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	1552000.0	1501000.0	1478000.0	1441000.0	4104000.0	1932000.0	1435000.0	1245000.0	1241000.0	1164000.0
Percentage of DepreciationNonRealEstateAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DispositionsSalesPrice us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:PropertyPlantAndEquipmentByType

krc:DispositionsSalesPrice

krc:A1800OwensStreetSanFranciscoCA, us-gaap:Building

Period End	2021-03-31
Value	1080
Percentage of DispositionsSalesPrice	100.0

krc:GroundLeaseMinimumRentIncreaseFiveYearsPercentageofAnnualPercentageRent

Period End	2021-06-30	2021-03-31
Value	0	5.0
Percentage of GroundLeaseMinimumRentIncreaseFiveYearsPercentageofAnnualPercentageRent	0.0	100.0

krc:InterestIncomeAndOtherNetInvestmentGainLoss

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30
Value	1337000.0	1373000.0	1845000.0	1869000.0	2838000.0	-3128000.0	1436000.0	761000.0	616000.0	1828000.0	-1706000.0	342000.0	771000.0	34000.0	1874000.0	1526000.0	1038000.0	1065000.0	644000.0	538000.0	311000.0	271000.0	66000.0	-694000.0	511000.0
Percentage of InterestIncomeAndOtherNetInvestmentGainLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:InterestIncomeAndOtherNetInvestmentGainLoss dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	1337000.0	1373000.0	1845000.0	1869000.0	2838000.0	-3128000.0	1436000.0	761000.0	616000.0	1828000.0	-1706000.0	342000.0	771000.0	34000.0	1874000.0	1526000.0	1038000.0
Percentage of InterestIncomeAndOtherNetInvestmentGainLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:NetIncomeLossAttributabletoNoncontrollingInterestinConsolidatedSubsidiary

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31
Value	6.687	4.894	3.798	4.258	4.367	4.896	4.079	3.6	4.15	4.191	3.485	3.219	3.64	3.974	3.421	2.984	3.242	3.133	1.937	1.027	0.216	0.195	-0.184	0.0	0.0	0.0
Percentage of NetIncomeLossAttributabletoNoncontrollingInterestinConsolidatedSubsidiary	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0

krc:NetIncomeLossAvailabletoCommonStockholdersBasicandDiluted

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	35	497	78	48	19	39	71	43	41	36	159	33	27	35	28	66	29	25	26	50	29	170	24	101	53	39	27	15	26	96	18	5.134	6.209	-1.321	28	-3.161
Percentage of NetIncomeLossAvailabletoCommonStockholdersBasicandDiluted	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:NetIncomeLossAvailabletoCommonStockholdersBasicandDiluted dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	35	502	79	49	19	39	73	44	42	36	162	34	27	36	28	67	29
Percentage of NetIncomeLossAvailabletoCommonStockholdersBasicandDiluted	101.0	101.0	101.3	101.4	101.2	101.5	101.7	101.7	101.7	101.7	101.9	101.7	101.7	101.8	101.7	102.0	101.8

krc:NoncashAmortizationOfDeferredRevenueRelatedToTenantFundedTenantImprovements

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	4.711	4.204	4.433	4.321	4.373	4.42	4.243	6.766	4.364	3.817	4.749	4.811	4.588	4.281	4.373	4.151	4.548	3.695	3.544	3.6	3.212	2.888	3.381	3.653	3.291	3.013	3.284	2.678	2.664	2.353	3.128	2.626	2.517	2.442	2.285	2.386	2.204	2.261	16	-2.337	-2.342	-2.326	-2.581	-2.333	-2.423	-2.352
Percentage of NoncashAmortizationOfDeferredRevenueRelatedToTenantFundedTenantImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:NoncashAmortizationOfDeferredRevenueRelatedToTenantFundedTenantImprovements dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	4.711	4.204	4.433	4.321	4.373	4.42	4.243	6.766	4.364	3.817	4.749	4.811	4.588	4.281	4.373	4.151
Percentage of NoncashAmortizationOfDeferredRevenueRelatedToTenantFundedTenantImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:OperatingLeaseIncomeAdjustments

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31
Value	288000.0	-1035000.0	-1823000.0	-5894000.0	-6487000.0	-143000.0	-217000.0	2864000.0
Percentage of OperatingLeaseIncomeAdjustments	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:OperatingLeaseIncomeAdjustmentsTransitioningTenantstoCashBasis

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31
Value	-1.0	-1.8	5.9	-6.5
Percentage of OperatingLeaseIncomeAdjustmentsTransitioningTenantstoCashBasis	100.0	100.0	100.0	100.0

krc:OperatingLeaseRightofUseAssetAmortization

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31
Value	213000.0	211000.0	207000.0	205000.0	203000.0	162000.0	147000.0	144000.0
Percentage of OperatingLeaseRightofUseAssetAmortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:OperatingLeaseRightofUseAssetAmortization dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31
Value	213000.0	211000.0	207000.0	205000.0	203000.0	162000.0	147000.0	144000.0
Percentage of OperatingLeaseRightofUseAssetAmortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:ProvisionforDoubtfulAccountsIncludingTenantsLeaseAgreement

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31
Value	-0.289	1.035	4.792	1.824	5.894	6.487	0.252	-0.594	0.452	-3.543	-1.029	1.338	5.641	-0.265
Percentage of ProvisionforDoubtfulAccountsIncludingTenantsLeaseAgreement	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:ProvisionforDoubtfulAccountsIncludingTenantsLeaseAgreement dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31
Value	-0.289	1.035	4.792	1.824	5.894	6.487	0.252	-0.594	0.452	-3.543	-1.029	1.338	5.641	-0.265
Percentage of ProvisionforDoubtfulAccountsIncludingTenantsLeaseAgreement	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodGrantDateFairValue us-gaap:AwardType

krc:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodGrantDateFairValue

krc:A2021PerformanceBasedRSUs

Period End	2021-02-18
Value	10
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodGrantDateFairValue	100.0

krc:TimeBasedRestrictedStockUnitsRSUsGrant

Period End	2021-02-28	2020-01-31
Value	9.1	9.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodGrantDateFairValue	0.0	0.0

krc:TenantImprovementsFundedDirectlyByTenantsToThirdParties

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	1.695	2.57	2.474	1.908	5.129	2.081	0.014	3.237	4.335	2.682	6.757	2.6	2.597	2.014	4.953	1.14	1.805	7.416	1.247	6.09	0.049	10	0.893	-0.092	12	0.231	19	7.032	11	4.47	1.883	-1.323	5.647	1.426	1.416	6.465	9.743	0.095	0.251	0.01	0.227	2.8	2.238	0.574	1.289	0.657
Percentage of TenantImprovementsFundedDirectlyByTenantsToThirdParties	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:TenantImprovementsFundedDirectlyByTenantsToThirdParties dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	1.695	2.57	2.474	1.908	5.129	2.081	0.014	3.237	4.335	2.682	6.757	2.6	2.597	2.014	4.953	1.14
Percentage of TenantImprovementsFundedDirectlyByTenantsToThirdParties	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalOther us-gaap:StatementEquityComponents

us-gaap:AdjustmentsToAdditionalPaidInCapitalOther

us-gaap:AdditionalPaidInCapital

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-0.102	0.256	-0.033	-0.181	-6.094	-3.059	-0.16	0.279	-0.241	-0.212	-1.359	0.335	-0.331	-0.103	-0.132	-2.936	-5.849	-3.308	0.021	18	-0.072	-2.657	-0.394	-1.496	-0.496	0.065	-0.031	-3.964	-0.089	-1.893	-0.262	1.752	-0.372	-4.578	-6.678	0.046	3.215	0.008	-0.059	-9.65
Percentage of AdjustmentsToAdditionalPaidInCapitalOther	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	0.102	-0.256	0.033	0.181	6.094	3.059	0.16	-0.279	0.241	0.212	1.359	-0.335	0.331	0.103	0.132	2.936	5.849	3.308	-0.021	-18.109	0.072	2.657	0.394	1.496	0.496	-0.065	0.031	3.964	0.089	1.893	0.262	-1.752	0.372	4.578	6.678	-0.046	-3.215	-0.008	0.059	9.65
Percentage of AdjustmentsToAdditionalPaidInCapitalOther	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0	-100.0

us-gaap:Parent

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-0.102	0.256	-0.033	-0.181	-6.094	-3.059	-0.16	0.279	-0.241	-0.212	-1.359	0.335	-0.331	-0.103	-0.132	-2.936	-5.849	-3.308	0.021	18	-0.072	-2.657	-0.394	-1.496	-0.496	0.065	-0.031	-3.964	-0.089	-1.893	-0.262	1.752	-0.372	-4.578	-6.678	0.046	3.215	0.008	-0.059	-9.65
Percentage of AdjustmentsToAdditionalPaidInCapitalOther	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AmortizationOfAboveAndBelowMarketLeases

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30
Value	-1013000.0	-1181000.0	-1334000.0	-1769000.0	-1914000.0	-2586000.0	-2965000.0	-1826000.0	-2321000.0	-2094000.0	-2101000.0	-2166000.0	-2938000.0	-2543000.0	-2502000.0	-2423000.0	-1191000.0	-2412000.0	-2038000.0	-1885000.0	-1640000.0	-1603000.0	-1680000.0	-1740000.0	-3101000.0	-1928000.0	-2112000.0	-1766000.0	-2716000.0	-1734000.0	-1762000.0	-1938000.0	-2030000.0	-2047000.0	-2083000.0	-2027000.0	-2064000.0	-525000.0	-463000.0	121000.0
Percentage of AmortizationOfAboveAndBelowMarketLeases	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AmortizationOfAboveAndBelowMarketLeases dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-1013000.0	-1181000.0	-1334000.0	-1769000.0	-1914000.0	-2586000.0	-2965000.0	-1826000.0	-2321000.0	-2094000.0	-2101000.0	-2166000.0	-2938000.0	-2543000.0	-2502000.0	-2423000.0
Percentage of AmortizationOfAboveAndBelowMarketLeases	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AmortizationOfFinancingCostsAndDiscounts

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	0.796	0.794	0.706	1.176	0.571	0.505	0.516	0.194	0.582	0.135	0.268	0.234	0.267	0.315	0.849	0.929	0.731	0.738	0.7	0.714	0.697	0.609	0.441	0.523	0.435	0.454	0.752	1.126	1.181	1.256	1.268	1.382	1.252	1.413	1.355	1.768	2.334	2.976	3.376	3.28	3.434	3.45	3.392	3.348	2.826	2.924
Percentage of AmortizationOfFinancingCostsAndDiscounts	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AmortizationOfFinancingCostsAndDiscounts dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	0.796	0.794	0.706	1.176	0.571	0.505	0.516	0.194	0.582	0.135	0.268	0.234	0.267	0.315	0.849	0.929
Percentage of AmortizationOfFinancingCostsAndDiscounts	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AssetAcquisitionConsiderationTransferred us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:AssetAcquisitionConsiderationTransferred

krc:A200West6thStreetAustinTX

Period End	2021-06-23
Value	580
Percentage of AssetAcquisitionConsiderationTransferred	100.0

krc:A2045PacificHighwaySanDiegoCA

Period End	2021-06-22
Value	42
Percentage of AssetAcquisitionConsiderationTransferred	0.0

us-gaap:AssetAcquisitionConsiderationTransferred us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty, us-gaap:SubsequentEventType

krc:A601108thAvenueNEBellevueWA, us-gaap:SubsequentEvent

Period End	2021-07-08
Value	47
Percentage of AssetAcquisitionConsiderationTransferred	0.0

us-gaap:CapitalExpendituresIncurredButNotYetPaid

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	27	57	34	22	2.641	129	14	18	42	87	16	61	23	57	11	37	16	50	-14.572	26	-8.972	59	20	23	-19.904	85	-15.602	-2.769	30	64	-6.384	21	16	42	45
Percentage of CapitalExpendituresIncurredButNotYetPaid	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:CapitalExpendituresIncurredButNotYetPaid dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	27	57	34	22	2.641	129	14	18	42	87	16	61	23	57	11	37
Percentage of CapitalExpendituresIncurredButNotYetPaid	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ConversionOfStockAmountConverted1

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	33	0.129	3.762	0.081	0.0	0.0	0.0	0.078	0.0	1.717	0.001	0.244	0.0	0.0	0.0	10	8.854	0.0	0.0	0.039	0.756	0.151	0.0	0.316	0.0	0.0	0.0	0.028	0.45	0.0	0.0	0.0	0.0
Percentage of ConversionOfStockAmountConverted1	100.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	0.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0	100.0	100.0	0.0	0.0	0.0	0.0

us-gaap:DepreciationAndAmortization

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	73	75	72	71	80	74	69	69	68	66	64	62	64	62	60	62	62	60	56	56	53	50	51	49	51	51	53	50	50	49	50	47	49	50	46	44	40	36	35	36	32	29	29	29	23	20
Percentage of DepreciationAndAmortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DepreciationAndAmortization dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	73	75	72	71	80	74	69	69	68	66	64	62	64	62	60	62	62
Percentage of DepreciationAndAmortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DividendsCommonStock

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	59	60	59	57	58	53	50	49	47	47	47	44	43	43	43	39	220	36	35	33	33	33	32	31	31	30	30	29	29	29	27	27	27	27	25	24	21	21	21	19	19	19	19	15
Percentage of DividendsCommonStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DividendsCommonStock us-gaap:StatementEquityComponents

us-gaap:AccumulatedDistributionsInExcessOfNetIncome

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	58	60	58	56	57	52	49	48	46	46	46	44	42	42	42	38	215	35	34	32	32	32	31	31	30	29	29	29	29	29	26	26	26	26	24	24	20	20	20	18	18	18	18	15
Percentage of DividendsCommonStock	99.0	99.1	98.4	98.4	98.3	98.2	98.1	98.1	98.1	98.1	98.0	98.0	98.0	98.0	98.0	98.0	97.5	97.3	97.2	97.3	98.1	98.1	98.0	98.0	98.0	97.9	97.9	97.9	97.9	97.9	97.7	97.7	97.7	97.6	97.6	97.6	97.2	97.2	97.2	96.9	96.9	96.8	96.9	96.2

us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	0.576	0.575	0.965	0.939	0.98	0.981	0.981	0.921	0.921	0.922	0.943	0.879	0.882	0.883	0.883	0.779	5.418	0.986	0.988	0.92	0.618	0.626	0.628	0.627	0.63	0.634	0.628	0.634	0.638	0.637	0.638	0.639	0.639	0.639	0.601	0.603	0.601	0.601	0.601	0.603	0.603	0.603	0.604	0.603
Percentage of DividendsCommonStock	1.0	0.9	1.6	1.6	1.7	1.8	1.9	1.9	1.9	1.9	2.0	2.0	2.0	2.0	2.0	2.0	2.5	2.7	2.8	2.7	1.9	1.9	2.0	2.0	2.0	2.1	2.1	2.1	2.1	2.1	2.3	2.3	2.3	2.4	2.4	2.4	2.8	2.8	2.8	3.1	3.1	3.2	3.1	3.8

us-gaap:Parent

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	58	60	58	56	57	52	49	48	46	46	46	44	42	42	42	38	215	35	34	32	32	32	31	31	30	29	29	29	29	29	26	26	26	26	24	24	20	20	20	18	18	18	18	15
Percentage of DividendsCommonStock	99.0	99.1	98.4	98.4	98.3	98.2	98.1	98.1	98.1	98.1	98.0	98.0	98.0	98.0	98.0	98.0	97.5	97.3	97.2	97.3	98.1	98.1	98.0	98.0	98.0	97.9	97.9	97.9	97.9	97.9	97.7	97.7	97.7	97.6	97.6	97.6	97.2	97.2	97.2	96.9	96.9	96.8	96.9	96.2

us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	1700000.0	1700000.0	1700000.0	1800000.0	2000000.0	1900000.0	1600000.0	700000.0	1900000.0	1600000.0	2200000.0	1500000.0	2800000.0	1500000.0	1900000.0	1700000.0	1600000.0	2000000.0	1600000.0	1500000.0	1300000.0	1200000.0	1000000.0	700000.0	900000.0	700000.0	800000.0	600000.0	500000.0	400000.0	300000.0	200000.0	200000.0	200000.0	900000.0	200000.0	200000.0	200000.0	300000.0	300000.0	300000.0	300000.0	300000.0	300000.0	300000.0
Percentage of EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ExtinguishmentOfDebtAmount dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:LongtermDebtType

us-gaap:ExtinguishmentOfDebtAmount

krc:KilroyRealtyL.P., krc:OneHundredFiftyMillionTermLoanFacility, us-gaap:LineOfCredit

Period End	2020-08-31
Value	150
Percentage of ExtinguishmentOfDebtAmount	100.0

us-gaap:GainLossOnSaleOfPropertyPlantEquipment

Period End	2021-06-30	2021-03-31	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30
Value	0.543	457	0.0	29	0.0	7.169	142	0.0	0.0	0.0	0.0	37	0.0	2.257	0.0	18	0.0	145	0.0	78	31	17	-3.49	0.0	3.49	0.0	0.0	0.0	0.0
Percentage of GainLossOnSaleOfPropertyPlantEquipment	100.0	100.0	0.0	100.0	0.0	100.0	100.0	0.0	0.0	0.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0	0.0

us-gaap:GainLossOnSaleOfPropertyPlantEquipment dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30	2017-06-30
Value	0.543	457	0.0	29	0.0	7.169	142	0.0	0.0	0.0	37	0.0
Percentage of GainLossOnSaleOfPropertyPlantEquipment	100.0	100.0	0.0	100.0	0.0	100.0	100.0	0.0	0.0	0.0	100.0	0.0

us-gaap:GainLossOnSaleOfPropertyPlantEquipment us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:PropertyPlantAndEquipmentByType

krc:A1800OwensStreetSanFranciscoCA, us-gaap:Building

Period End	2021-03-31
Value	457
Percentage of GainLossOnSaleOfPropertyPlantEquipment	100.0

us-gaap:GeneralPartnersCapitalAccountDistributionAmount dei:LegalEntity

us-gaap:GeneralPartnersCapitalAccountDistributionAmount

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	59	60	59	57	58	53	50	49	47	47	47	44	43	43
Percentage of GeneralPartnersCapitalAccountDistributionAmount	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:GeneralPartnersCapitalAccountDistributionAmount dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	59	60	59	57	58	-53.189	50	49	47	47	47	44	43	43
Percentage of GeneralPartnersCapitalAccountDistributionAmount	100.0	100.0	100.0	100.0	100.0	-100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInOperatingAssets

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31
Value	5.332	-1.71	-0.56	18	-6.025	-7.966	-10.276	9.212	7.158	8.382	-1.233	3.65	0.873	4.64	0.762	9.552	5.607	1.811	-2.049	1.192	7.632	-1.561	-1.271	0.256	0.679	8.421	-1.162	-4.254	-0.9	5.949	-1.82	0.307	-1.262	7.39	-1.232	-1.789	0.449	3.869	1.108	1.833	0.677	1.816
Percentage of IncreaseDecreaseInOperatingAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInOperatingAssets dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	5.332	-1.71	-0.56	18	-6.025	-7.966	-10.276	9.212	7.158	8.382	-1.233	3.65	0.873	4.64	0.762	9.552
Percentage of IncreaseDecreaseInOperatingAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInOperatingLiabilities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31
Value	-29.077	29	-19.816	47	-7.772	8.209	-20.246	48	-19.595	15	11	35	-1.998	3.598	-18.96	17	-2.216	9.791	4.054	25	-12.566	2.71	-4.11	16	-5.578	5.545	-9.038	29	2.24	-5.701	-2.707	26	-2.683	18	-14.645	24	-7.671	14	-15.717	26	-20.899	12
Percentage of IncreaseDecreaseInOperatingLiabilities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInOperatingLiabilities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	-29.077	29	-19.816	47	-7.772	8.209	-20.246	48	-19.595	15	11	35	-1.998	3.598	-18.96	17
Percentage of IncreaseDecreaseInOperatingLiabilities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestCostsCapitalized

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30	2017-06-30	2017-03-31	2016-09-30	2016-06-30	2016-03-31	2015-09-30	2015-06-30	2015-03-31
Value	17	16	18	19	20	19	19	18	18	15	13	11	10	9.829	10	11	13	14	12	10
Percentage of InterestCostsCapitalized	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestCostsCapitalized dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30
Value	17	16	18	19	20	19	19	18	18	15	13	11
Percentage of InterestCostsCapitalized	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestCostsCapitalizedAdjustment dei:LegalEntity

us-gaap:InterestCostsCapitalizedAdjustment

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	18	16	18	19	20	21	20	20	20	19	19	19	15	13	13	12	10
Percentage of InterestCostsCapitalizedAdjustment	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestCostsIncurred dei:LegalEntity

us-gaap:InterestCostsIncurred

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	39	39	39	38	36	35	34	32	32	30	31	30	28	27	28	28	28
Percentage of InterestCostsIncurred	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest dei:LegalEntity, us-gaap:Ownership

us-gaap:LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest

krc:NonAffiliatedInvestors, krc:OperatingPartnership

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30
Value	1.0	1.0	-0.6	1.583	0	0.017	0	-0.001	0	0.02	0.02	0.02
Percentage of LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest	100.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	100.0	100.0

us-gaap:LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest us-gaap:Ownership

krc:OperatingPartnership

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30
Value	99.0	99.0	0.6	97.417	0	0.983	0	0.001	0	0.98	0.98	0.98
Percentage of LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest	9900.0	9900.0	-100.0	6153.9	0.0	5782.4	0.0	-100.0	0.0	4900.0	4900.0	4900.0

us-gaap:MarketableSecuritiesGainLossExcludingOtherThanTemporaryImpairments

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	1261000.0	1305000.0	1770000.0	1658000.0	2662000.0	-3226000.0	987000.0	673000.0	544000.0	1681000.0	-2140000.0	271000.0	422000.0	-404000.0	1304000.0	536000.0	512000.0	671000.0	263000.0	481000.0	249000.0	137000.0	-98000.0	-681000.0	122000.0	388000.0	-110000.0	-39000.0	392000.0	154000.0	494000.0	669000.0	-30000.0	356000.0	128000.0	315000.0	-155000.0	435000.0	276000.0	-642000.0	26000.0	187000.0	245000.0	311000.0	-322000.0
Percentage of MarketableSecuritiesGainLossExcludingOtherThanTemporaryImpairments	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:MinorityInterestDecreaseFromRedemptions dei:LegalEntity, us-gaap:StatementEquityComponents

us-gaap:MinorityInterestDecreaseFromRedemptions

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2020-09-30
Value	-6034000.0
Percentage of MinorityInterestDecreaseFromRedemptions	100.0

krc:KilroyRealtyL.P., us-gaap:NoncontrollingInterest

Period End	2020-09-30
Value	6034000.0
Percentage of MinorityInterestDecreaseFromRedemptions	-100.0

us-gaap:NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	354000.0	4886000.0	1012000.0	785000.0	367000.0	705000.0	1343000.0	852000.0	871000.0	700000.0	3185000.0	691000.0	566000.0	751000.0	590000.0	1394000.0	616000.0	623000.0	743000.0	1453000.0	829000.0	3610000.0	489000.0	1945000.0	1090000.0	815000.0	578000.0	321000.0	603000.0	2087000.0	419000.0	131000.0	157000.0	-22000.0	4479000.0	-67000.0
Percentage of NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeaseCost

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30
Value	0.883	0.692	0.721	0.986	1.33	1.456	2.016	1.192	2.65	1.757	0.0
Percentage of OperatingLeaseCost	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0

us-gaap:OperatingLeaseCost dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-03-31
Value	0.883	0.692	0.721	0.986	1.33	1.456	2.016	1.192	2.65	1.757	0.0	0.0
Percentage of OperatingLeaseCost	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0

us-gaap:OperatingLeaseExpense

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	2023000.0	1828000.0	2125000.0	2119000.0	2330000.0	2317000.0	1978000.0	2049000.0	2114000.0	1972000.0
Percentage of OperatingLeaseExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeaseExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	2023000.0	1828000.0	2125000.0	2119000.0	2330000.0	2317000.0	1978000.0	2049000.0	2114000.0	1972000.0
Percentage of OperatingLeaseExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeaseLeaseIncome

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	224	234	228	227	218	218	217	212	197	199
Percentage of OperatingLeaseLeaseIncome	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeaseLeaseIncome dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	224	234	228	227	218	218	217	212	197	199
Percentage of OperatingLeaseLeaseIncome	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeaseLeaseIncomeLeasePayments

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	197	204	201	197	194	193	181	181	173	168
Percentage of OperatingLeaseLeaseIncomeLeasePayments	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeasePayments

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31
Value	1432000.0	1455000.0	1058000.0	1781000.0	1573000.0	1332000.0	1307000.0	1218000.0	1479000.0	1220000.0	1249000.0	1110000.0	1239000.0
Percentage of OperatingLeasePayments	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeasePayments dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31
Value	1432000.0	1455000.0	1058000.0	1781000.0	1573000.0	1332000.0	1307000.0	1218000.0	1479000.0	1220000.0	1249000.0	1110000.0	1239000.0
Percentage of OperatingLeasePayments	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OperatingLeaseVariableLeaseIncome

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	26	31	31	31	29	31	33	30	24	27
Percentage of OperatingLeaseVariableLeaseIncome	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OtherCostAndExpenseOperating

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	40	38	39	39	37	38	42	41	38	38
Percentage of OtherCostAndExpenseOperating	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OtherCostAndExpenseOperating dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	40	38	39	39	37	38	42	41	38	38
Percentage of OtherCostAndExpenseOperating	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	371000.0	365000.0	572000.0	572000.0	542000.0	543000.0	537000.0	530000.0	543000.0	509000.0	512000.0	507000.0	514000.0	471000.0	515000.0	501000.0	511000.0	448000.0	2595000.0	426000.0	423000.0	395000.0	434000.0	367000.0	418000.0	415000.0	414000.0	432000.0	426000.0	427000.0	397000.0	450000.0	1689000.0
Percentage of ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	371000.0	365000.0	572000.0	572000.0	542000.0	543000.0	537000.0	530000.0	543000.0	509000.0	512000.0	507000.0	514000.0	471000.0	515000.0	501000.0	511000.0
Percentage of ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PartnersCapitalAccountPublicSaleOfUnits dei:LegalEntity

us-gaap:PartnersCapitalAccountPublicSaleOfUnits

krc:KilroyRealtyL.P.

Period End	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30
Value	-0.074	-0.045	721	353	-0.051	6.597	124	17	-0.02
Percentage of PartnersCapitalAccountPublicSaleOfUnits	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PartnersCapitalAccountPublicSaleOfUnits dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30
Value	-0.074	-0.045	721	353	-0.051	6.597	124	17	-0.02
Percentage of PartnersCapitalAccountPublicSaleOfUnits	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PartnersCapitalAccountTreasuryUnitsPurchases dei:LegalEntity

us-gaap:PartnersCapitalAccountTreasuryUnitsPurchases

krc:KilroyRealtyL.P.

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	21	3.353	0.735	9.799	1.652	0.793	12	0.0	2.911	0.0	13	0.0	1.344
Percentage of PartnersCapitalAccountTreasuryUnitsPurchases	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0

us-gaap:PartnersCapitalAccountTreasuryUnitsPurchases dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	21	3.353	0.735	9.799	-1.652	0.793	12	0.0	2.911	0.0	13	0.0	1.344
Percentage of PartnersCapitalAccountTreasuryUnitsPurchases	100.0	100.0	100.0	100.0	-100.0	100.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0

us-gaap:PartnersCapitalAccountUnitBasedCompensation dei:LegalEntity

us-gaap:PartnersCapitalAccountUnitBasedCompensation

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	645000.0	1950000.0	1101000.0	805000.0	1720000.0	839000.0	820000.0	2210000.0	628000.0	845000.0	589000.0	1864000.0	599000.0	600000.0
Percentage of PartnersCapitalAccountUnitBasedCompensation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PartnersCapitalAccountUnitBasedCompensation dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	645000.0	1950000.0	1101000.0	805000.0	1720000.0	839000.0	820000.0	2210000.0	628000.0	845000.0	589000.0	1864000.0	599000.0	600000.0
Percentage of PartnersCapitalAccountUnitBasedCompensation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsForCapitalImprovements

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	35	28	40	8.834	36	44	48	37	29	31	58	33	38	35	26	21	19	21	30	16	39	25	27	20	26	24	38	27	34	32	45	33	24	25	25
Percentage of PaymentsForCapitalImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsForCapitalImprovements dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	35	28	40	8.834	36	44	48	37	29	31	58	33	38	35	26	21
Percentage of PaymentsForCapitalImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsOfFinancingCosts

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	7.334	0.235	0.378	3.933	2.123	0.16	1.13	4.213	0.393	0.942	3.984	0.438	1.38	0.46	4.02	5.289	0.325	1.866	0.674	0.806	0.342	0.337	0.28	3.765	0.372	0.397	0.605	4.137	3.488	0.418	0.409	0.428	0.677	2.87	2.567	1.752	1.767	1.877	0.476	3.383	4.041	1.16	3.712	6.557	4.074	0.569
Percentage of PaymentsOfFinancingCosts	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsOfFinancingCosts dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	7.334	0.235	0.378	3.933	2.123	0.16	1.13	4.213	0.393	0.942	3.984	0.438	1.38	0.46	4.02	5.289
Percentage of PaymentsOfFinancingCosts	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	0.0	21	0.195	3.353	0.735	9.799	0.287	1.651	0.488	12	0.0	2.911	0.0	13	0.0	1.344	0.628	11	2.001	0.991	0.264	5.619	3.96	1.285	0.015	1.821	0.672	0.329	1.015	1.517	0.707	0.135	0.469	1.209	0.925	0.133	0.0	0.603	0.416	0.004	0.0	0.732	0.0	1.296
Percentage of PaymentsRelatedToTaxWithholdingForShareBasedCompensation	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0

us-gaap:PaymentsRelatedToTaxWithholdingForShareBasedCompensation dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	0.0	21	0.195	3.353	0.735	9.799	0.287	1.651	0.488	12	0.0	2.911	0.0	13	0.0	1.344
Percentage of PaymentsRelatedToTaxWithholdingForShareBasedCompensation	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0

us-gaap:PaymentsToDevelopRealEstateAssets

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	90	172	100	92	126	167	290	182	191	181	177	107	92	111	126	109	93	67	128	60	98	63	96	112	109	89	124	131	88	73	97	96	51	73	30	26	12	13	9.835	6.335	5.633	6.714	7.151	6.568	3.751	4.362
Percentage of PaymentsToDevelopRealEstateAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsToDevelopRealEstateAssets dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	90	172	100	92	126	167	290	182	191	181	177	107	92	111	126	109
Percentage of PaymentsToDevelopRealEstateAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsToMinorityShareholders

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30
Value	4.717	11	6.884	1.448	4.307	2.608	2.108	3.032	1.511	6.301	4.789	0.529	4.315	2.17	4.308	3.583	3.923	4.728	2.476	0.858	0.281	0.0	0.0	0.0
Percentage of PaymentsToMinorityShareholders	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0

us-gaap:PaymentsToMinorityShareholders dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	4.717	11	6.884	1.448	4.307	2.608	2.108	3.032	1.511	6.301	4.789	0.529	4.315	2.17	4.308	3.583
Percentage of PaymentsToMinorityShareholders	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ProceedsFromIssuanceOfCommonStock

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2017-01-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-0.01	-0.074	469	252	-0.182	353	-0.051	6.597	124	0.0	17	-0.02	-0.017	308	308	31	0.0	0.0	0.0	-0.111	249	24	113	80	0.0	22	0.0	0.0	307	19	23	9.731	253	26	382	12	0.0	221	0.0	0.0	0.0
Percentage of ProceedsFromIssuanceOfCommonStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0

us-gaap:ProceedsFromIssuanceOfCommonStock dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2018-12-31	2018-09-30	2017-12-31	2017-09-30
Value	-0.01	-0.074	-0.045	721	-0.182	353	-0.051	6.597	17	-0.02
Percentage of ProceedsFromIssuanceOfCommonStock	100.0	100.0	-0.0	286.4	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ProceedsFromIssuanceOfCommonStock us-gaap:StatementEquityComponents, us-gaap:SubsidiarySaleOfStock

us-gaap:CommonStock, krc:ForwardEquitySale

Period End	2020-09-30
Value	0.0
Percentage of ProceedsFromIssuanceOfCommonStock	-0.0

us-gaap:ProceedsFromIssuanceOfCommonStock us-gaap:SubsidiarySaleOfStock

krc:ForwardEquitySale

Period End	2020-09-30	2020-06-30	2020-03-25	2020-03-31	2019-07-31	2018-08-31
Value	0.0	0.0	474	247	354	354
Percentage of ProceedsFromIssuanceOfCommonStock	-0.0	0.0	98.1	0.0	0.0	0.0

us-gaap:ProceedsFromIssuanceOfUnsecuredDebt

Period End	2020-12-31	2020-09-30	2019-12-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	0.0	422	0.0	499	598	50	0.0	0.0	424	0.0	0.0	250	0.0	0.0	0.0	0.0	0.0	0.0	395	0.0	0.0	0.0	0.0	0.0	299	0.0	0.0	0.0	150	0.0	324	0.0	0.0	324	0.0
Percentage of ProceedsFromIssuanceOfUnsecuredDebt	0.0	100.0	0.0	100.0	100.0	100.0	0.0	0.0	100.0	0.0	0.0	100.0	0.0	0.0	0.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0	100.0	0.0	100.0	0.0	0.0	100.0	0.0

us-gaap:ProceedsFromIssuanceOfUnsecuredDebt dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2020-12-31	2020-09-30	2019-12-31	2019-09-30	2018-12-31	2018-09-30	2017-12-31	2017-09-30
Value	0.0	422	0.0	499	598	50	424	0.0
Percentage of ProceedsFromIssuanceOfUnsecuredDebt	0.0	100.0	0.0	100.0	100.0	100.0	100.0	0.0

us-gaap:ProceedsFromLongTermLinesOfCredit

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	0.0	0.0	0.0	190	480	205	235	190	120	140	415	90	200	70	0.0	0.0	0.0	35	190	80	0.0	0.0	100	150	140	160	115	90	45	10.0	0.0	0.0	286	165	223	30	248	0.0	260	42	107	265	225	63
Percentage of ProceedsFromLongTermLinesOfCredit	0.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ProceedsFromLongTermLinesOfCredit dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	0.0	0.0	0.0	190	480	205	235	190	120	140	415	90	200	70
Percentage of ProceedsFromLongTermLinesOfCredit	0.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ProceedsFromSaleOfRealEstateHeldforinvestment

Period End	2021-06-30	2021-03-31	2019-12-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31
Value	0.542	1012	107	0.0	364	0.0	0.0	0.0	0.0	170	0.0	11	0.0	48	14	262	0.0	153	140	25	59	14	43	309	6.769	0.0	14	0.0	121	-1.351	42	100	64	0.0	0.0	0.0
Percentage of ProceedsFromSaleOfRealEstateHeldforinvestment	100.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0	0.0	100.0	0.0	100.0	0.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0

us-gaap:ProceedsFromSaleOfRealEstateHeldforinvestment dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2019-12-31	2019-09-30	2018-12-31	2018-09-30	2017-12-31	2017-09-30
Value	0.542	1012	107	0.0	364	0.0	0.0	170
Percentage of ProceedsFromSaleOfRealEstateHeldforinvestment	100.0	100.0	100.0	0.0	100.0	0.0	0.0	100.0

us-gaap:RealEstateTaxExpense

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	22	25	24	23	21	22	21	19	17	18	18	17	17	17	15	16	16	17	15	14	13	11	12	12	12	12	12	11	10	11	10	10	10	10	9.341	9.312	8.881	8.389	7.643	8.36	8.413	8.169	7.459	7.582	6.482	6.036
Percentage of RealEstateTaxExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateTaxExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Value	22	25	24	23	21	22	21	19	17	18	18	17	17	17	15	16	16
Percentage of RealEstateTaxExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RepaymentsOfLongTermLinesOfCredit

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2010-03-31
Value	0.0	0.0	380	55	235	580	45	50	405	105	170	10.0	260	10.0	0.0	0.0	0.0	255	45	5.0	0.0	100	130	160	0.0	250	25	135	0.0	10.0	0.0	185	128	240	121	212	66	245	72	144	153	210	225	10.0
Percentage of RepaymentsOfLongTermLinesOfCredit	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RepaymentsOfLongTermLinesOfCredit dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	0.0	0.0	380	55	235	580	45	50	405	105	170	10.0	260	10.0
Percentage of RepaymentsOfLongTermLinesOfCredit	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RepaymentsOfSecuredDebt

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30
Value	1.329	1.316	1.303	1.291	1.277	1.266	0.465	0.46	0.454	74	0.914	0.902	0.89	0.878	124	1.527	1.508	2.705	66	2.446	2.431	2.377	92	2.564	36	28	2.53	2.456	2.445	2.414	2.39	4.07	2.31	84	1.684	1.324	101	1.546	122	1.892
Percentage of RepaymentsOfSecuredDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RepaymentsOfSecuredDebt dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	1.329	1.316	1.303	1.291	1.277	1.266	0.465	0.46	0.454	74	0.914	0.902	0.89	0.878	124	1.527
Percentage of RepaymentsOfSecuredDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RepaymentsOfUnsecuredDebt

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2011-12-31	2010-12-31
Value	0.0	261	330	0.0	325	0.0	0.0	0.0
Percentage of RepaymentsOfUnsecuredDebt	0.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0

us-gaap:RepaymentsOfUnsecuredDebt dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2020-12-31	2018-12-31	2017-12-31
Value	0.0	261	330
Percentage of RepaymentsOfUnsecuredDebt	0.0	100.0	100.0

us-gaap:SeveranceCosts1 us-gaap:IncomeStatementLocation

us-gaap:SeveranceCosts1

us-gaap:GeneralAndAdministrativeExpense

Period End	2020-12-31	2020-09-30	2020-06-30
Value	0.0	0.0	14
Percentage of SeveranceCosts1	0.0	0.0	100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod us-gaap:AwardType, us-gaap:SubsequentEventType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod

krc:PerformanceBasedRSUs, us-gaap:SubsequentEvent

Period End	2020-07-31
Value	12263.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	100.0

krc:TimeBasedRestrictedStockUnitsRsus, us-gaap:SubsequentEvent

Period End	2020-07-31
Value	1514.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	12.3

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

krc:A2021PerformanceBasedRSUs

Period End	2021-02-18
Value	63.93
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue us-gaap:TitleOfIndividual, us-gaap:AwardType

krc:OneParticipant, krc:A2021PerformanceBasedRSUs

Period End	2021-02-18
Value	66.95
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	104.7

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate

krc:A2021PerformanceBasedRSUs

Period End	2021-02-18
Value	35.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate

krc:A2021PerformanceBasedRSUs

Period End	2021-02-18
Value	0.2
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	100.0

us-gaap:StockIssuedDuringPeriodValueConversionOfUnits us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueConversionOfUnits

us-gaap:AdditionalPaidInCapital

Period End	2020-09-30	2020-06-30	2020-03-31	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2012-12-31	2011-12-31	2011-09-30
Value	0.129	3.761	0.081	0.078	0.0	1.717	0.0	0.244	0.0	0.0	0.0	10	8.852	0.0	0.0	0.039	0.756	0.151	0.0	0.316	0.0	0.0	0.0	0.028	0.0	0.0	0.0
Percentage of StockIssuedDuringPeriodValueConversionOfUnits	100.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	0.0	0.0	0.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0

us-gaap:NoncontrollingInterest

Period End	2020-09-30	2020-06-30	2020-03-31	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2012-12-31	2011-12-31	2011-09-30
Value	-0.129	-3.762	-0.081	-0.078	0.0	-1.717	-0.001	-0.244	0.0	0.0	0.0	-10.939	-8.854	0.0	0.0	-0.039	-0.756	-0.151	0.0	-0.316	0.0	0.0	0.0	-0.028	0.0	0.0	0.0
Percentage of StockIssuedDuringPeriodValueConversionOfUnits	-100.0	-100.0	-100.0	-100.0	0.0	-100.0	0.0	-100.0	0.0	0.0	0.0	-100.0	-100.0	0.0	0.0	-100.0	-100.0	-100.0	0.0	-100.0	0.0	0.0	0.0	-100.0	0.0	0.0	0.0

us-gaap:Parent

Period End	2020-09-30	2020-06-30	2020-03-31	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2012-12-31	2011-12-31	2011-09-30
Value	0.129	3.762	0.081	0.078	0.0	1.717	0.001	0.244	0.0	0.0	0.0	10	8.854	0.0	0.0	0.039	0.756	0.151	0.0	0.316	0.0	0.0	0.0	0.028	0.0	0.0	0.0
Percentage of StockIssuedDuringPeriodValueConversionOfUnits	100.0	100.0	100.0	100.0	0.0	100.0	0.0	100.0	0.0	0.0	0.0	100.0	100.0	0.0	0.0	100.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardGross us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardGross

us-gaap:AdditionalPaidInCapital

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31
Value	-8000.0	-1000.0	0	-3000.0	-1000.0	-4000.0	0	0	0	-4000.0	0	0	0	-3000.0	0	0	0	-1000.0	-1000.0	0	0	0	-1000.0	0	0	0	-10000.0	0	20000.0	-10000.0
Percentage of StockIssuedDuringPeriodValueRestrictedStockAwardGross	100.0	100.0	0.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0	100.0	100.0	0.0	0.0	0.0	100.0	0.0	0.0	0.0	100.0	0.0	100.0	100.0

us-gaap:CommonStock

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30
Value	8000.0	1000.0	0	3000.0	1000.0	4000.0	0	0	0	4000.0	0	0	0	3000.0	0	0
Percentage of StockIssuedDuringPeriodValueRestrictedStockAwardGross	-100.0	-100.0	0.0	-100.0	-100.0	-100.0	0.0	0.0	0.0	-100.0	0.0	0.0	0.0	-100.0	0.0	0.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	645000.0	1950000.0	1101000.0	805000.0	1720000.0	839000.0	820000.0	2210000.0	628000.0	845000.0	589000.0	1864000.0	599000.0	600000.0	527000.0	4164000.0	488000.0	486000.0	449000.0	404000.0	424000.0	424000.0	431000.0	413000.0	411000.0	408000.0	373000.0	373000.0	366000.0	336000.0	334000.0
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	645000.0	1950000.0	1101000.0	805000.0	1720000.0	839000.0	820000.0	2210000.0	628000.0	845000.0	589000.0	1864000.0	599000.0	600000.0	527000.0	4164000.0	488000.0	486000.0	449000.0	404000.0	424000.0	424000.0	431000.0	413000.0	411000.0	408000.0	373000.0	373000.0	366000.0	336000.0	334000.0
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:Parent

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	645000.0	1950000.0	1101000.0	805000.0	1720000.0	839000.0	820000.0	2210000.0	628000.0	845000.0	589000.0	1864000.0	599000.0	600000.0	527000.0	4164000.0	488000.0	486000.0	449000.0	404000.0	424000.0	424000.0	431000.0	413000.0	411000.0	408000.0	373000.0	373000.0	366000.0	336000.0	334000.0
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StockRepurchasedAndRetiredDuringPeriodValue

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-03-31
Value	21	3.353	0.735	9.799	1.652	0.793	12	2.911	13
Percentage of StockRepurchasedAndRetiredDuringPeriodValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StockRepurchasedAndRetiredDuringPeriodValue us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-03-31
Value	21	3.352	0.735	9.798	1.651	0.793	12	2.911	13
Percentage of StockRepurchasedAndRetiredDuringPeriodValue	100.0	100.0	100.0	100.0	99.9	100.0	100.0	100.0	100.0

us-gaap:CommonStock

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-03-31	2018-03-31
Value	0.003	0.001	0.0	0.001	0.001	0.001	0.002
Percentage of StockRepurchasedAndRetiredDuringPeriodValue	0.0	0.0	0.0	0.0	0.1	0.0	0.0

us-gaap:Parent

Period End	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-03-31
Value	21	3.353	0.735	9.799	1.652	0.793	12	2.911	13
Percentage of StockRepurchasedAndRetiredDuringPeriodValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StraightLineRent

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30
Value	13	17	15	18	13	19	23	18	17	12	10	5.727	5.207	5.359	7.738	10.0	7.926	7.611	6.773	4.319	9.086	9.451	8.853	6.955	8.883	19	16	7.452	3.834	3.959	5.947	6.103	5.361	6.724	5.097	5.858	5.088	5.487	5.788	6.637
Percentage of StraightLineRent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StraightLineRent dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	13	17	15	18	13	19	23	18	17	12	10	5.727	5.207	5.359	7.738	10.0
Percentage of StraightLineRent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:VariableLeaseCost

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	600000.0	400000.0	600000.0	700000.0	900000.0	900000.0	600000.0	700000.0	800000.0	700000.0
Percentage of VariableLeaseCost	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:WeightedAverageNumberDilutedSharesOutstandingAdjustment

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30	2017-06-30	2017-03-31	2016-09-30	2016-06-30	2016-03-31	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-09-30	2011-06-30	2011-03-31	2010-09-30
Value	465530.0	457010.0	441330.0	454830.0	514340.0	518730.0	837190.0	541790.0	551560.0	459160.0	469390.0	559470.0	551910.0	630020.0	693390.0	614830.0	510020.0	488720.0	519680.0	537590.0	1949100.0	2324500.0	2015500.0	0	1967300.0	0	0	0	0	0	0	0	0	0
Percentage of WeightedAverageNumberDilutedSharesOutstandingAdjustment	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	100.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:WeightedAverageNumberDilutedSharesOutstandingAdjustment dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-09-30	2017-06-30
Value	465530.0	457010.0	441330.0	454830.0	514340.0	518730.0	837190.0	541790.0	551560.0	459160.0	469390.0	559470.0	551910.0
Percentage of WeightedAverageNumberDilutedSharesOutstandingAdjustment	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:AcquisitionRelatedIntangibleLiabilitiesNet

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	13	24	29	30	41	32	34	36	40	43	44	47	51	49	53	53	57	59	62	55	45	36	37	29	16
Percentage of AcquisitionRelatedIntangibleLiabilitiesNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:AllowanceForDeferredRentReceivables

Period End	2020-12-31	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	804000.0	1552000.0	3339000.0	4855000.0	3594000.0	3225000.0	3238000.0	2970000.0	2611000.0	2252000.0	1524000.0	1526000.0	1527000.0	1540000.0	1882000.0	2116000.0	2116000.0	2155000.0	1989000.0	1989000.0	1990000.0	1990000.0	2075000.0	1973000.0	2127000.0	2127000.0	2607000.0	2632000.0	2848000.0	3008000.0	3406000.0	3462000.0	3822000.0	3831000.0
Percentage of AllowanceForDeferredRentReceivables	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:AllowanceforDoubtfulAccountsPremiumsandOtherReceivablesAfterAdjustment

Period End	2020-12-31	2019-12-31	2018-12-31
Value	1700000.0	700000.0	2900000.0
Percentage of AllowanceforDoubtfulAccountsPremiumsandOtherReceivablesAfterAdjustment	100.0	100.0	100.0

krc:AtMarketStockAggregateGrossSalesPriceofCommonStock us-gaap:StatementEquityComponents

krc:AtMarketStockAggregateGrossSalesPriceofCommonStock

krc:IssuanceOfEquityUnderAtmProgram

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31	2014-12-31
Value	252	133	17	32	300
Percentage of AtMarketStockAggregateGrossSalesPriceofCommonStock	100.0	100.0	100.0	100.0	100.0

krc:AtMarketStockOfferingProgramRemainedAvailableForIssuance us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents, us-gaap:SubsidiarySaleOfStock

krc:AtMarketStockOfferingProgramRemainedAvailableForIssuance

us-gaap:CommonStock, krc:A2018AtTheMarketProgram, krc:ForwardEquitySale

Period End	2020-12-31	2019-03-31
Value	214	399
Percentage of AtMarketStockOfferingProgramRemainedAvailableForIssuance	100.0	100.0

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedThereafter us-gaap:DeferredRevenueArrangementType

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedThereafter

krc:TenantFundedTenantImprovements

Period End	2020-12-31
Value	23
Percentage of ContractWithCustomerLiabilityFutureAmortizationRecognizedThereafter	100.0

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearFive us-gaap:DeferredRevenueArrangementType

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearFive

krc:TenantFundedTenantImprovements

Period End	2020-12-31
Value	8564000.0
Percentage of ContractWithCustomerLiabilityFutureAmortizationRecognizedYearFive	100.0

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearFour us-gaap:DeferredRevenueArrangementType

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearFour

krc:TenantFundedTenantImprovements

Period End	2020-12-31
Value	11
Percentage of ContractWithCustomerLiabilityFutureAmortizationRecognizedYearFour	100.0

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearOne us-gaap:DeferredRevenueArrangementType

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearOne

krc:TenantFundedTenantImprovements

Period End	2020-12-31
Value	16
Percentage of ContractWithCustomerLiabilityFutureAmortizationRecognizedYearOne	100.0

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearThree us-gaap:DeferredRevenueArrangementType

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearThree

krc:TenantFundedTenantImprovements

Period End	2020-12-31
Value	13
Percentage of ContractWithCustomerLiabilityFutureAmortizationRecognizedYearThree	100.0

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearTwo us-gaap:DeferredRevenueArrangementType

krc:ContractWithCustomerLiabilityFutureAmortizationRecognizedYearTwo

krc:TenantFundedTenantImprovements

Period End	2020-12-31
Value	15
Percentage of ContractWithCustomerLiabilityFutureAmortizationRecognizedYearTwo	100.0

krc:ContractwithCustomerLiabilityOther

Period End	2020-12-31	2019-12-31	2018-12-31
Value	26	19	15
Percentage of ContractwithCustomerLiabilityOther	100.0	100.0	100.0

krc:DeferredLeasingCostsAndAcquisitionRelatedIntangibleAssetsNet

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	184	190	210	208	209	204	212	202	203	187	197	183	186	181	183	185	195	202	208	180	186	186	176	173	174	182	201	183	178	188	186	190	188	196	189	187	168	158	155	155	153	129	131	51
Percentage of DeferredLeasingCostsAndAcquisitionRelatedIntangibleAssetsNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DeferredLeasingCostsAndAcquisitionRelatedIntangibleAssetsNet dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	184	190	210	208	209	204	212	202	203	187	197	183	186	183
Percentage of DeferredLeasingCostsAndAcquisitionRelatedIntangibleAssetsNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DeferredRentReceivablesGross

Period End	2020-12-31	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	387	339	270	265	260	254	249	241	236	228	220	213	209	200	191	185	178	170	158	141	136	132	129	123	126	124	118	112	113	109	104	107	101	92
Percentage of DeferredRentReceivablesGross	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DisposalGroupIncludingDiscontinuedOperationAdvanceRentIncludingTenantSecurityDeposits

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2018-12-31
Value	62	68	68	61	63	65	66	57	60
Percentage of DisposalGroupIncludingDiscontinuedOperationAdvanceRentIncludingTenantSecurityDeposits	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DisposalGroupIncludingDiscontinuedOperationAdvanceRentIncludingTenantSecurityDeposits dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2018-12-31
Value	62	68	68	61	63	65	66	57	60
Percentage of DisposalGroupIncludingDiscontinuedOperationAdvanceRentIncludingTenantSecurityDeposits	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DisposalGroupIncludingDiscontinuedOperationDeferredRevenueAndAcquisitionRelatedIntangibleLiabilities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2018-12-31
Value	122	123	128	131	129	130	139	134	149
Percentage of DisposalGroupIncludingDiscontinuedOperationDeferredRevenueAndAcquisitionRelatedIntangibleLiabilities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:DisposalGroupIncludingDiscontinuedOperationDeferredRevenueAndAcquisitionRelatedIntangibleLiabilities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2018-12-31
Value	122	123	128	131	129	130	139	134	149
Percentage of DisposalGroupIncludingDiscontinuedOperationDeferredRevenueAndAcquisitionRelatedIntangibleLiabilities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:FiniteLivedIntangibleLiabilitiesAmortizationExpenseNextRollingTwelveMonths krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:FiniteLivedIntangibleLiabilitiesAmortizationExpenseNextRollingTwelveMonths

krc:BelowMarketLease

Period End	2020-12-31	2018-12-31	2017-12-31
Value	4152000.0	7779000.0	9456000.0
Percentage of FiniteLivedIntangibleLiabilitiesAmortizationExpenseNextRollingTwelveMonths	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesaccumulatedamortization krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesaccumulatedamortization

krc:BelowMarketLease

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	13	27	29	40	33	31	29	28	27	26	28	30	30	31	28	28	25	24	17
Percentage of Finitelivedintangibleliabilitiesaccumulatedamortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesamortizationexpenseafteryearfive krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesamortizationexpenseafteryearfive

krc:BelowMarketLease

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30
Value	3.018	6.733	2.65	4.808	0.425	0.425	0.425	0.425	2.473	2.473	2.473	2.473	6.023	6.023	6.023	4.556	9.081
Percentage of Finitelivedintangibleliabilitiesamortizationexpenseafteryearfive	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesamortizationexpenseyearfive krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesamortizationexpenseyearfive

krc:BelowMarketLease

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30
Value	710000.0	988000.0	790000.0	1031000.0	2169000.0	2169000.0	2035000.0	2035000.0	3597000.0	3597000.0	3597000.0	3597000.0	5177000.0	5177000.0	5177000.0	4525000.0	6127000.0
Percentage of Finitelivedintangibleliabilitiesamortizationexpenseyearfive	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesamortizationexpenseyearfour krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesamortizationexpenseyearfour

krc:BelowMarketLease

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30
Value	812000.0	1486000.0	1253000.0	3676000.0	4581000.0	4583000.0	3574000.0	3574000.0	5735000.0	5735000.0	5735000.0	5735000.0	6780000.0	6780000.0	6780000.0	6127000.0	7195000.0
Percentage of Finitelivedintangibleliabilitiesamortizationexpenseyearfour	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesamortizationexpenseyearthree krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesamortizationexpenseyearthree

krc:BelowMarketLease

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30
Value	1.486	1.938	3.942	6.519	7.159	7.159	5.713	5.713	7.017	7.016	7.337	7.337	7.847	7.847	7.847	7.195	9.385
Percentage of Finitelivedintangibleliabilitiesamortizationexpenseyearthree	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesamortizationexpenseyeartwo krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesamortizationexpenseyeartwo

krc:BelowMarketLease

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30
Value	3.167	4.621	6.854	9.116	8.438	8.437	6.997	7.017	7.638	7.638	8.189	8.403	9.567	9.577	9.577	9.385	11
Percentage of Finitelivedintangibleliabilitiesamortizationexpenseyeartwo	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesgross krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesgross

krc:BelowMarketLease

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	26	51	53	65	69	56	57	52	53	55	59	64	68	69	69	73	69	70	70
Percentage of Finitelivedintangibleliabilitiesgross	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:Finitelivedintangibleliabilitiesnet krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

krc:Finitelivedintangibleliabilitiesnet

krc:BelowMarketLease

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	13	24	23	24	35	25	27	24	26	28	30	34	37	38	41	45	43	46	52
Percentage of Finitelivedintangibleliabilitiesnet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:NetBookValueOfPropertiesPledgedAsCollateralForSecuredDebt dei:LegalEntity, us-gaap:LongtermDebtType

krc:NetBookValueOfPropertiesPledgedAsCollateralForSecuredDebt

krc:KilroyRealtyL.P., us-gaap:SecuredDebt

Period End	2020-12-31
Value	222
Percentage of NetBookValueOfPropertiesPledgedAsCollateralForSecuredDebt	100.0

krc:OperatingLeaseLeaseIncomeAllowanceForDoubtfulAccountsCOVID19Related

Period End	2020-12-31
Value	600000.0
Percentage of OperatingLeaseLeaseIncomeAllowanceForDoubtfulAccountsCOVID19Related	100.0

krc:RealEstatePropertiesPercentageLeased us-gaap:MajorPropertyClass

krc:RealEstatePropertiesPercentageLeased

krc:OfficeProperties

Period End	2020-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31
Value	94.3	0.962	0.96	0.957	0.97
Percentage of RealEstatePropertiesPercentageLeased	100.0	100.0	100.0	100.0	100.0

krc:RealEstatePropertiesPercentageLeased us-gaap:PropertyPlantAndEquipmentByType

krc:OfficeProperties

Period End	2021-06-30	2021-03-31	2020-09-30
Value	93.6	93.3	95.5
Percentage of RealEstatePropertiesPercentageLeased	0.0	0.0	0.0

krc:RealEstatePropertiesPercentageOccupied us-gaap:MajorPropertyClass

krc:RealEstatePropertiesPercentageOccupied

krc:OfficeProperties

Period End	2020-12-31	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2015-12-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31
Value	91.2	0.935	0.946	0.921	0.938	0.925	0.944	0.935	0.94	0.943	0.952	0.94	0.939	0.941	0.96	0.948	0.944	0.941	0.936	0.924	0.934
Percentage of RealEstatePropertiesPercentageOccupied	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:StabilizedResidentialProperties

Period End	2020-12-31	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31
Value	72.0	0.935	0.824	0.785	0.734	0.728	0.797	0.833	0.833	0.83	0.702	0.72	0.77	0.649	0.46
Percentage of RealEstatePropertiesPercentageOccupied	78.9	100.0	87.1	85.2	78.3	78.7	84.4	89.1	88.6	88.0	73.7	76.6	82.0	69.0	47.9

krc:RealEstatePropertiesPercentageOccupied us-gaap:PropertyPlantAndEquipmentByType

krc:OfficeProperties

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30
Value	91.8	91.5	92.2	0.923
Percentage of RealEstatePropertiesPercentageOccupied	0.0	0.0	0.0	0.0

krc:StabilizedResidentialProperties

Period End	2020-09-30	2020-06-30
Value	87.8	0.893
Percentage of RealEstatePropertiesPercentageOccupied	0.0	0.0

krc:SharebasedCompensationArrangementbySharebasedPaymentAwardNumberofSharesRequested us-gaap:AwardDate

krc:SharebasedCompensationArrangementbySharebasedPaymentAwardNumberofSharesRequested

krc:ShareholderMeetingDateMay212015

Period End	2020-12-31
Value	10
Percentage of SharebasedCompensationArrangementbySharebasedPaymentAwardNumberofSharesRequested	100.0

krc:UndevelopedLandAndConstructionInProgress

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2010-12-31
Value	2318	1771	1778	1938	2109	2318	2296	1892	1827	2131	2058	2146	1993	1530	1432	1292	1183	1087	1013	945	894	1018	1361	1475	1363	1265	1120	1112	1270	1047	1016	907	808	747	809	668	557	446	430	328	290
Percentage of UndevelopedLandAndConstructionInProgress	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:UndevelopedLandAndConstructionInProgress dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	2318	1771	1778	1938	2109	2318	2296	1892	1827	2131	2058	2146	1993	1432
Percentage of UndevelopedLandAndConstructionInProgress	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

srt:RealEstateAndAccumulatedDepreciationAmountOfEncumbrances

Period End	2020-12-31	2019-12-31	2018-12-31
Value	254	259	335
Percentage of RealEstateAndAccumulatedDepreciationAmountOfEncumbrances	100.0	100.0	100.0

srt:RealEstateAndAccumulatedDepreciationAmountOfEncumbrances us-gaap:MortgageLoansOnRealEstateDescriptionTypeOfProperty

krc:OperatingProperties

Period End	2020-12-31
Value	254
Percentage of RealEstateAndAccumulatedDepreciationAmountOfEncumbrances	100.0

srt:RealEstateAndAccumulatedDepreciationAmountOfEncumbrances us-gaap:MortgageLoansOnRealEstateDescriptionTypeOfProperty, us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

srt:OfficeBuilding, krc:A320WestlakeAve.NorthWAAnd321TerryAvenueNorthLakeUnionWA

Period End	2020-12-31	2019-12-31
Value	87	89
Percentage of RealEstateAndAccumulatedDepreciationAmountOfEncumbrances	34.4	34.5

srt:OfficeBuilding, krc:WOlympicBoulevardLosAngelesCalifornia

Period End	2020-12-31	2019-12-31
Value	166	170
Percentage of RealEstateAndAccumulatedDepreciationAmountOfEncumbrances	65.6	65.5

srt:RealEstateFederalIncomeTaxBasis

Period End	2020-12-31
Value	8600
Percentage of RealEstateFederalIncomeTaxBasis	100.0

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	429	408	445	458	401	417	418	439	385	373	374	360	278	223	249	271	219	215	202	252	211	265	246	249	199	217	225	243	215	187	198	210	184	171	154	127	98	92	81	93	66	78	68	52
Percentage of AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	429	408	445	458	401	417	418	439	385	373	374	360	278	249
Percentage of AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AccountsReceivableGrossCurrent

Period End	2020-12-31	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31
Value	13	27	24	21	19	19	19	20	15	15	15	11	11	11	13
Percentage of AccountsReceivableGrossCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AccountsReceivableNet

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	9.773	12	12	16	20	16	26	34	27	28	20	17	15	17	16	18	13	13	13	9.709	10	9.54	11	11	8.956	8.122	7.229	6.443	10	11	10	11	10	10	9.22	7.113	7.643	6.99	8.395	6.86	4.732	4.816	6.258	3.236
Percentage of AccountsReceivableNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AccountsReceivableNet dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	9.773	12	12	16	20	16	26	34	27	28	20	17	15	16
Percentage of AccountsReceivableNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AccrualForEnvironmentalLossContingencies us-gaap:EnvironmentalRemediationContingency

us-gaap:AccrualForEnvironmentalLossContingencies

krc:EnvironmentalMatters

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2019-12-31	2018-12-31	2017-12-31
Value	77	72	71	72	80	83	28
Percentage of AccrualForEnvironmentalLossContingencies	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AccrualForEnvironmentalLossContingencies us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

krc:A2045PacificHighwaySanDiegoCA

Period End	2021-06-22
Value	5.2
Percentage of AccrualForEnvironmentalLossContingencies	0.0

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent

Period End	2020-12-31	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31
Value	1799000.0	1171000.0	4639000.0	4155000.0	4358000.0	2028000.0	2309000.0	2120000.0	1458000.0	2216000.0	1712000.0	1725000.0	1818000.0	2080000.0	2080000.0
Percentage of AllowanceForDoubtfulAccountsReceivableCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AreaOfLand us-gaap:MajorPropertyClass

us-gaap:AreaOfLand

krc:DevelopmentSites

Period End	2020-12-31
Value	61.0
Percentage of AreaOfLand	100.0

us-gaap:AreaOfLand us-gaap:PropertyPlantAndEquipmentByType

krc:DevelopmentSites

Period End	2021-06-30	2021-03-31	2020-09-30
Value	59.0	63.0	61.0
Percentage of AreaOfLand	0.0	0.0	0.0

us-gaap:AreaOfRealEstateProperty krc:AssetAcquisition, us-gaap:StatementGeographical, us-gaap:MajorPropertyClass

us-gaap:AreaOfRealEstateProperty

krc:DevelopmentProjectInHollywood, krc:HollywoodCalifornia, krc:StabilizedOfficeProperties

Period End	2020-12-31
Value	361390.0
Percentage of AreaOfRealEstateProperty	100.0

krc:DevelopmentProjectInSanDiegoCalifornia, krc:SanDiegoCalifornia, krc:StabilizedRetailSpace

Period End	2020-12-31
Value	95871.0
Percentage of AreaOfRealEstateProperty	26.5

krc:DevelopmentProjectinSanFrancisco, krc:SanFranciscoCalifornia, krc:StabilizedOfficeProperties

Period End	2020-12-31
Value	750370.0
Percentage of AreaOfRealEstateProperty	207.6

us-gaap:AssetsFairValueDisclosure us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:AssetsFairValueDisclosure

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	25	24	27	25	23	19	27	26	25	24	21	23	22	20
Percentage of AssetsFairValueDisclosure	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ContractWithCustomerLiability

Period End	2020-12-31	2019-12-31	2018-12-31
Value	88	96	104
Percentage of ContractWithCustomerLiability	100.0	100.0	100.0

us-gaap:ContractWithCustomerLiability us-gaap:DeferredRevenueArrangementType

krc:TenantFundedTenantImprovements

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	88	96	104	104
Percentage of ContractWithCustomerLiability	100.0	100.0	100.0	0.0

us-gaap:DebtInstrumentCarryingAmount dei:LegalEntity

us-gaap:DebtInstrumentCarryingAmount

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2019-12-31	2018-12-31	2018-09-30	2018-06-30
Value	3951	3953	3954	3955	3579	2955	2891	2807
Percentage of DebtInstrumentCarryingAmount	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DebtInstrumentCarryingAmount dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:LongtermDebtType

krc:KilroyRealtyL.P., krc:A2500UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	425
Percentage of DebtInstrumentCarryingAmount	10.7

krc:KilroyRealtyL.P., krc:A3.050UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	500	500	0.0
Percentage of DebtInstrumentCarryingAmount	12.6	14.0	0.0

krc:KilroyRealtyL.P., krc:A4.300UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	50	50	50	0.0
Percentage of DebtInstrumentCarryingAmount	1.3	1.4	1.7	0.0

krc:KilroyRealtyL.P., krc:A4.350UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	200	200	200	0.0
Percentage of DebtInstrumentCarryingAmount	5.1	5.6	6.8	0.0

krc:KilroyRealtyL.P., krc:A4.750UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	400	400	400	0.0
Percentage of DebtInstrumentCarryingAmount	10.1	11.2	13.5	0.0

krc:KilroyRealtyL.P., krc:A4270UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	350
Percentage of DebtInstrumentCarryingAmount	8.9

krc:KilroyRealtyL.P., krc:FourPointFortyEightPercentMortgagePayableDueJulyOneTwoThousandTwentySeven, us-gaap:SecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	87	89	91	93
Percentage of DebtInstrumentCarryingAmount	2.2	2.5	3.1	0.0

krc:KilroyRealtyL.P., krc:ThreePointFiveSevenMortgagePayabledueDecemberTwoZeroTwoSix, us-gaap:SecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	166	170	170	170
Percentage of DebtInstrumentCarryingAmount	4.2	4.7	5.8	0.0

us-gaap:DebtInstrumentFairValue us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType

us-gaap:DebtInstrumentFairValue

us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:SecuredDebt

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31
Value	278	272	282	268	269	236	272	271	271	264	335	331	336	339	346	467	467	468	469	383	387	388	391
Percentage of DebtInstrumentFairValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:UnsecuredDebt

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31
Value	4014	3931	4089	4024	3591	3247	3252	3245	2702	2622	2546	2173	2145	2162	2077	1983	2172	2163	1900	1982	1987	1948	1898	536	593	601
Percentage of DebtInstrumentFairValue	1439.6	1445.0	1447.3	1498.7	1331.5	1370.5	1191.3	1196.7	995.2	993.3	758.1	656.0	636.8	636.8	598.9	423.9	464.3	461.8	405.0	516.6	512.3	502.0	484.9	0.0	0.0	0.0

us-gaap:DebtInstrumentFairValue us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType

us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:SecuredDebt

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31
Value	251	252	253	254	256	257	258	259	259	259	335	336	338	339	340	465	467	469	472	370	373	378	380
Percentage of DebtInstrumentFairValue	90.0	92.7	89.7	94.9	95.0	108.6	94.7	95.5	95.6	98.4	99.9	101.7	100.4	100.0	98.3	99.5	100.0	100.2	100.8	96.6	96.3	97.4	97.2

us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:UnsecuredDebt

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31
Value	3672	3671	3670	3668	3399	3050	3049	3048	2553	2552	2552	2207	2156	2155	2006	1909	2097	2096	1847	1846	1845	1845	1844
Percentage of DebtInstrumentFairValue	1316.7	1349.4	1298.9	1366.4	1260.3	1287.1	1116.9	1123.9	940.4	966.9	759.8	666.2	640.2	634.8	578.4	408.0	448.3	447.4	393.7	481.2	475.8	475.5	471.0

us-gaap:DebtInstrumentInterestRateEffectivePercentage dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:LongtermDebtType

us-gaap:DebtInstrumentInterestRateEffectivePercentage

krc:KilroyRealtyL.P., krc:A2500UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	2.56
Percentage of DebtInstrumentInterestRateEffectivePercentage	100.0

krc:KilroyRealtyL.P., krc:A3.050UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31
Value	3.064	0.03064
Percentage of DebtInstrumentInterestRateEffectivePercentage	119.7	0.0

krc:KilroyRealtyL.P., krc:A3.350UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	3.35	0.0335	0.0335
Percentage of DebtInstrumentInterestRateEffectivePercentage	130.9	0.0	0.0

krc:KilroyRealtyL.P., krc:A3.450UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	3.47	0.0347	0.0347
Percentage of DebtInstrumentInterestRateEffectivePercentage	135.5	0.0	0.0

krc:KilroyRealtyL.P., krc:A3.450UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	3.45	0.0345	0.0345
Percentage of DebtInstrumentInterestRateEffectivePercentage	134.8	0.0	0.0

krc:KilroyRealtyL.P., krc:A3.800UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	3.8	0.038	0.038
Percentage of DebtInstrumentInterestRateEffectivePercentage	148.4	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.250UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	4.35	0.0435	0.0435
Percentage of DebtInstrumentInterestRateEffectivePercentage	169.9	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.300UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	4.3	0.043	0.043
Percentage of DebtInstrumentInterestRateEffectivePercentage	168.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.350UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	4.35	0.0435	0.0435
Percentage of DebtInstrumentInterestRateEffectivePercentage	169.9	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.375UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	4.444	0.04444	0.04444
Percentage of DebtInstrumentInterestRateEffectivePercentage	173.6	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.750UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	4.8	0.048	0.048
Percentage of DebtInstrumentInterestRateEffectivePercentage	187.5	0.0	0.0

krc:KilroyRealtyL.P., krc:A4270UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	4.27
Percentage of DebtInstrumentInterestRateEffectivePercentage	166.8

krc:KilroyRealtyL.P., krc:FourPointFortyEightPercentMortgagePayableDueJulyOneTwoThousandTwentySeven, us-gaap:SecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	4.48	0.0448	0.0448
Percentage of DebtInstrumentInterestRateEffectivePercentage	175.0	0.0	0.0

krc:KilroyRealtyL.P., krc:ThreePointFiveSevenMortgagePayabledueDecemberTwoZeroTwoSix, us-gaap:SecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	3.57	0.0357	0.0357
Percentage of DebtInstrumentInterestRateEffectivePercentage	139.5	0.0	0.0

us-gaap:DebtInstrumentUnamortizedDiscount dei:LegalEntity, us-gaap:LongtermDebtType

us-gaap:DebtInstrumentUnamortizedDiscount

krc:KilroyRealtyL.P., us-gaap:SeniorNotes

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2019-09-30	2018-12-31
Value	7.7	8.0	8.3	8.5	6.7	6.6
Percentage of DebtInstrumentUnamortizedDiscount	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DebtInstrumentUnamortizedDiscount us-gaap:DebtInstrument, us-gaap:LongtermDebtType

krc:A2.500UnsecuredSeniorNotes, us-gaap:SeniorNotes

Period End	2020-08-31
Value	2.7
Percentage of DebtInstrumentUnamortizedDiscount	0.0

us-gaap:DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:LongtermDebtType

us-gaap:DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet

krc:KilroyRealtyL.P., krc:A2500UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	6332000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	100.0

krc:KilroyRealtyL.P., krc:A3.050UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	5399000.0	5998000.0	0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	85.3	0.0	0.0

krc:KilroyRealtyL.P., krc:A3.350UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	709000.0	825000.0	941000.0	1056000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	11.2	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A3.450UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	2321000.0	2907000.0	3493000.0	4047000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	36.7	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A3.450UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	347000.0	390000.0	432000.0	475000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	5.5	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A3.800UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	560000.0	834000.0	1108000.0	1382000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	8.8	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.250UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	4567000.0	5100000.0	5632000.0	6164000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	72.1	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.300UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	246000.0	290000.0	342000.0	0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	3.9	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.350UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	1012000.0	1186000.0	1375000.0	0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	16.0	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.375UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	2631000.0	3185000.0	3738000.0	4292000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	41.6	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A4.750UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	3952000.0	4446000.0	4960000.0	0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	62.4	0.0	0.0	0.0

krc:KilroyRealtyL.P., krc:A4270UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	1825000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	28.8

us-gaap:DebtInstrumentUnamortizedDiscountPremiumNet dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:LongtermDebtType

us-gaap:DebtInstrumentUnamortizedDiscountPremiumNet

krc:KilroyRealtyL.P., krc:A2500UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-08-31
Value	2700000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumNet	100.0

us-gaap:DebtInstrumentUnamortizedDiscountPremiumNet us-gaap:LongtermDebtType

us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31
Value	8300000.0	6500000.0	6600000.0	6300000.0	-6600000.0	-7400000.0	5900000.0	1900000.0	2100000.0	2400000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumNet	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:DeferredCompensationLiabilityCurrentAndNoncurrent

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2015-06-30	2014-12-31	2013-12-31	2012-12-31
Value	27	27	21	20	14	12	12	11	9.9	7.3
Percentage of DeferredCompensationLiabilityCurrentAndNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DeferredRentReceivablesNet

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	384	370	386	375	358	352	337	314	297	280	267	261	256	251	246	238	233	225	218	212	207	199	189	183	176	168	156	139	134	130	127	121	124	122	115	110	110	106	101	103	97	93	89	74
Percentage of DeferredRentReceivablesNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DeferredRentReceivablesNet dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	384	370	386	375	358	352	337	314	297	280	267	261	256	246
Percentage of DeferredRentReceivablesNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DividendsPayableCurrentAndNoncurrent

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	59	59	59	59	57	57	53	53	50	47	47	47	47	43	43	43	44	38	222	37	37	35	34	34	33	33	32	31	31	31	31	31	29	29	28	28	25	26	22	22	22	20	20	17
Percentage of DividendsPayableCurrentAndNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DividendsPayableCurrentAndNoncurrent dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	59	59	59	59	57	57	53	53	50	47	47	47	47	43
Percentage of DividendsPayableCurrentAndNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DividendsPayableCurrentAndNoncurrent dei:LegalEntity, us-gaap:AwardType

krc:KilroyRealtyL.P., us-gaap:RestrictedStockUnitsRSU

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	0.838	0.82	0.797	0.651
Percentage of DividendsPayableCurrentAndNoncurrent	1.4	1.5	1.7	1.5

us-gaap:DividendsPayableCurrentAndNoncurrent dei:LegalEntity, us-gaap:PreferredUnitsByName

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	59	53	47	43
Percentage of DividendsPayableCurrentAndNoncurrent	100.0	100.0	100.0	100.0

krc:KilroyRealtyL.P., krc:PartnersCapitalGeneralPartner

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	58	51	45	41
Percentage of DividendsPayableCurrentAndNoncurrent	97.6	96.6	96.4	96.5

krc:KilroyRealtyL.P., krc:PartnersCapitalLimitedPartner

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	0.575	0.981	0.922	0.883
Percentage of DividendsPayableCurrentAndNoncurrent	1.0	1.8	1.9	2.0

us-gaap:DividendsPayableCurrentAndNoncurrent us-gaap:StatementClassOfStock

krc:CommonStockholdersAndNoncontrollingUnitholders

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	59	53	47	43	220	33	31	29	27	21	19
Percentage of DividendsPayableCurrentAndNoncurrent	100.0	100.0	100.0	100.0	99.3	95.3	95.0	94.6	94.1	94.7	94.1

us-gaap:CapitalUnits

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	0.575	0.981	0.922	0.883	5.418	0.618	0.631	0.632	0.639	0.601	0.603
Percentage of DividendsPayableCurrentAndNoncurrent	1.0	1.8	1.9	2.0	2.4	1.8	1.9	2.0	2.2	2.6	3.0

us-gaap:CommonStock

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	58	51	45	41	212	32	30	28	26	20	18
Percentage of DividendsPayableCurrentAndNoncurrent	97.6	96.6	96.4	96.5	95.4	92.3	91.8	91.3	90.7	90.7	89.9

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2019-12-31	2014-03-31
Value	41	47	35	42	50	36
Percentage of EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	104	100	100	101	89	85	81	77	72	74	72	74	74	71	70	68	63	59	58	62	61	55	53	52
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	25	31	36	46	40	39	37	34	33	32	35	43	43	44	45	44	42	44	40	31	34	26	20	15
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization	24.6	31.6	35.9	45.7	45.3	45.9	45.7	44.9	46.5	43.1	48.7	58.8	58.4	61.9	64.0	64.8	68.0	74.2	69.6	50.1	55.4	48.3	38.1	29.7

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	71	67	51	41	44	51	50	48	37	37	35	31	33	36	26	23	22	29	24	24	22	27	24
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	1.663	2.138	2.616	3.51	5.198	5.458	5.458	5.458	5.457	8.291	8.29	8.291	8.291	8.302	6.694	6.694	3.973	8.669	6.539	6.537	6.049	10	8.31
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	2.3	3.2	5.0	8.4	11.6	10.6	10.8	11.3	14.4	22.2	23.5	26.1	24.9	22.9	24.9	27.9	17.9	29.2	26.6	27.1	27.3	39.4	33.3

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	31	30	31	30	25	6.74	12	19	27	6.936	13	20	25	6.384	12	18	22
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	6.531	11	16	13	10	2.8	5.872	9.829	13	4.274	9.49	15	19	6.549	13	20	23
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	21.0	36.8	52.1	44.2	41.1	41.5	45.9	50.2	49.9	61.6	71.8	76.3	75.3	102.6	104.9	113.3	102.7

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFive krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFive

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	19	16	14	13	12	15	14	13	11	15	13	13	14	15	13	13	12	14	13	12	11	11	10
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	0.473	0.602	0.648	1.708	2.505	2.923	2.923	2.789	2.789	4.714	4.714	4.714	4.714	5.532	5.689	5.689	4.574	7.744	6.818	6.818	5.417	6.505	4.636
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	2.4	3.5	4.3	12.8	19.9	19.3	20.2	20.6	23.8	31.1	34.7	35.1	33.1	35.1	41.7	42.4	37.3	53.5	49.2	55.4	47.4	55.0	42.5

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFour krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFour

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	21	19	18	16	16	19	18	17	15	19	17	17	18	19	17	16	15	16	16	14	13	14	13
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	0.584	1.641	1.589	2.508	5.739	5.148	5.149	4.637	4.637	6.373	6.373	6.373	6.373	8.44	8.774	8.774	7.659	9.445	8.613	8.613	6.798	9.614	7.353
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	2.7	8.2	8.5	15.6	34.4	26.4	27.5	26.5	29.6	33.5	36.5	36.9	34.3	44.0	51.5	52.4	48.3	55.8	52.5	57.9	49.4	66.8	54.7

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearThree krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearThree

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	24	23	21	20	21	23	22	21	19	22	21	20	22	22	19	19	18	19	19	17	16	18	17
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	1.534	4.001	2.861	5.61	8.856	6.998	6.998	6.296	6.296	9.113	9.112	9.281	9.281	10	10	10	9.361	12	11	11	9.913	15	11
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	6.3	16.9	13.1	27.9	41.4	29.6	30.6	29.3	32.2	40.2	43.3	44.4	41.9	45.7	52.9	54.1	50.8	64.4	61.5	66.8	60.5	83.9	66.5

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	28	27	26	25	25	26	26	24	22	25	23	23	25	24	22	22	21	23	23	21	20	20	19
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	3.885	6.668	5.963	8.85	13	9.739	9.738	9.036	9.108	10	10	10	10	13	13	13	12	19	18	18	15	22	14
Percentage of FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	13.7	24.7	22.2	34.7	52.6	36.1	37.2	36.6	40.0	40.7	43.7	45.2	43.6	52.8	59.9	61.2	59.1	81.0	78.1	83.7	76.9	111.5	75.3

us-gaap:FiniteLivedIntangibleAssetsGross krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass

us-gaap:FiniteLivedIntangibleAssetsGross

krc:DeferredLeasingCosts

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	300	286	266	248	239	229	228	223	205	201	196	201	216	196	184	183	178	170	168	171	168	153	149	142
Percentage of FiniteLivedIntangibleAssetsGross	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeasesAcquiredInPlace

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	40	58	66	82	94	72	72	70	72	74	80	93	97	94	100	104	100	108	106	103	101	98	74	61
Percentage of FiniteLivedIntangibleAssetsGross	13.4	20.3	24.9	33.0	39.5	31.4	31.9	31.6	35.3	36.7	40.8	46.3	45.0	47.9	54.3	56.9	56.1	63.7	62.9	60.7	60.1	64.4	50.1	43.0

us-gaap:GeneralPartnersCapitalAccount dei:LegalEntity

us-gaap:GeneralPartnersCapitalAccount

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	5500	5512	5079	5051	5049	5074	4369	4340	3988	3987	4003	3876	3876	3773
Percentage of GeneralPartnersCapitalAccount	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InvestmentBuildingAndBuildingImprovements

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	6682	6480	6783	6535	6289	5997	5866	5770	5712	5300	5207	5056	5017	4987	4908	4871	4983	4962	4938	4669	4639	4501	4091	4028	3906	3880	4059	3882	3720	3706	3590	3527	3652	3631	3335	3169	3137	2970	2830	2881	2820	2470	2435	1920
Percentage of InvestmentBuildingAndBuildingImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InvestmentBuildingAndBuildingImprovements dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	6682	6480	6783	6535	6289	5997	5866	5770	5712	5300	5207	5056	5017	4908
Percentage of InvestmentBuildingAndBuildingImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LandAndLandImprovements

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2013-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	1551	1539	1628	1612	1546	1506	1466	1315	1284	1184	1160	1127	1127	1127	1076	1076	1108	1108	1108	1017	1020	978	875	850	839	838	877	757	675	657	635	637	612	562	576	537
Percentage of LandAndLandImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LandAndLandImprovements dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	1551	1539	1628	1612	1546	1506	1466	1315	1284	1184	1160	1127	1127	1076
Percentage of LandAndLandImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LesseeOperatingLeaseDiscountRate us-gaap:RealEstateAndAccumulatedDepreciationDescriptionOfProperty

us-gaap:LesseeOperatingLeaseDiscountRate

krc:A200West6thStreetAustinTX

Period End	2021-06-23
Value	3.97
Percentage of LesseeOperatingLeaseDiscountRate	100.0

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	7435000.0	5642000.0	5641000.0	5641000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	100.0	100.0	100.0	100.0

us-gaap:LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear

Period End	2021-06-30	2021-03-31	2020-09-30
Value	3699000.0	4230000.0	1411000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceived

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	6467	6322	7248	7418
Percentage of LessorOperatingLeasePaymentsToBeReceived	100.0	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceivedFiveYears

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	635	609	719	716
Percentage of LessorOperatingLeasePaymentsToBeReceivedFiveYears	100.0	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceivedFourYears

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	690	662	750	748
Percentage of LessorOperatingLeasePaymentsToBeReceivedFourYears	100.0	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceivedNextTwelveMonths

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	782	759	731	729
Percentage of LessorOperatingLeasePaymentsToBeReceivedNextTwelveMonths	100.0	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear

Period End	2021-06-30	2021-03-31	2020-09-30
Value	352	517	174
Percentage of LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceivedThereafter

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	2509	2334	3455	3453
Percentage of LessorOperatingLeasePaymentsToBeReceivedThereafter	100.0	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceivedThreeYears

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	728	699	788	790
Percentage of LessorOperatingLeasePaymentsToBeReceivedThreeYears	100.0	100.0	100.0	100.0

us-gaap:LessorOperatingLeasePaymentsToBeReceivedTwoYears

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	768	739	804	804
Percentage of LessorOperatingLeasePaymentsToBeReceivedTwoYears	100.0	100.0	100.0	100.0

us-gaap:LineOfCreditFacilityInterestRateAtPeriodEnd dei:LegalEntity, us-gaap:LongtermDebtType

us-gaap:LineOfCreditFacilityInterestRateAtPeriodEnd

krc:KilroyRealtyL.P., us-gaap:RevolvingCreditFacility

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	1.0	1.11	1.14	1.15	0.0116	0.0185	0.0276	0.0302	0.0341	0.035	0.0348	0.0323	0.031	0.0256
Percentage of LineOfCreditFacilityInterestRateAtPeriodEnd	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity dei:LegalEntity, us-gaap:LongtermDebtType

us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity

krc:KilroyRealtyL.P., us-gaap:RevolvingCreditFacility

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-06-30
Value	1100	750	750	750	750	750	750	750	750	750	750	750	750	750	600
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity dei:LegalEntity, us-gaap:LongtermDebtType

us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity

krc:KilroyRealtyL.P., us-gaap:RevolvingCreditFacility

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	1100	750	750	750	750	370	505	750	375	565	705	420	455	750
Percentage of LineOfCreditFacilityRemainingBorrowingCapacity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	2399	2399	2800	2800
Percentage of LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	100.0	100.0	100.0	100.0

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	5554000.0	5554000.0	5342000.0	5342000.0
Percentage of LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	100.0	100.0	100.0	100.0

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	401	401	406	406
Percentage of LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	100.0	100.0	100.0	100.0

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	406	406	431	431
Percentage of LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	100.0	100.0	100.0	100.0

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	431	431	305	305
Percentage of LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	100.0	100.0	100.0	100.0

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	305	305	5.554	5.554
Percentage of LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	100.0	100.0	100.0	100.0

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-09-30
Value	2698000.0	4026000.0	1304000.0
Percentage of LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear	100.0	100.0	100.0

us-gaap:MinorityInterestInOperatingPartnerships

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	53	53	49	83	83	87	81	81	78	78	78	76	78	77	77	77	77	77	85	93	89	89	57	57	54	53	51	51	51	51	49	50	46
Percentage of MinorityInterestInOperatingPartnerships	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:MinorityInterestOwnershipPercentageByNoncontrollingOwners dei:LegalEntity, us-gaap:Ownership

us-gaap:MinorityInterestOwnershipPercentageByNoncontrollingOwners

krc:NonAffiliatedInvestors, krc:OperatingPartnership

Period End	2020-12-31	2019-12-31
Value	1.0	1.9
Percentage of MinorityInterestOwnershipPercentageByNoncontrollingOwners	100.0	100.0

us-gaap:MinorityInterestOwnershipPercentageByNoncontrollingOwners us-gaap:Ownership

krc:NonAffiliatedInvestorsAndCertainExecutiveOfficersandDirectorsOfTheCompany

Period End	2020-12-31	2019-12-31
Value	1.0	1.9
Percentage of MinorityInterestOwnershipPercentageByNoncontrollingOwners	100.0	100.0

us-gaap:MinorityInterestOwnershipPercentageByParent us-gaap:Ownership

us-gaap:MinorityInterestOwnershipPercentageByParent

krc:A101FirstLLCand303SecondLLC

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30
Value	56.0	56.0	56.0	56.0	0.56	0.56	0.56	0.56	0.56	0.56	0.56
Percentage of MinorityInterestOwnershipPercentageByParent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

krc:OperatingPartnership

Period End	2020-12-31	2019-12-31	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30
Value	99.0	0.981	0.98	0.98	0.98	0.98	0.98	0.979	0.979	0.979
Percentage of MinorityInterestOwnershipPercentageByParent	176.8	175.2	175.0	175.0	0.0	175.0	0.0	0.0	0.0	0.0

krc:RedwoodLLC

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30
Value	93.0	93.0	93.0	93.0	0.93	0.93	0.93	0.93	0.93	0.93	0.93
Percentage of MinorityInterestOwnershipPercentageByParent	166.1	166.1	166.1	166.1	166.1	166.1	166.1	166.1	166.1	166.1	166.1

us-gaap:NetRentableArea

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2014-01-31	2013-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	14	13	13	13	14	0.114175	1.046394	1.046394	0.506571	14	0.079	0.079	0.079	0.079	0.200306	0.320398	0.320398	13	1.532764	0.794126
Percentage of NetRentableArea	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:NoncontrollingInterestInVariableInterestEntity

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	192	190	197	200	197	197	195	193	192	190	192	193	182	183	181	128	128	129	130	85	6.65	6.715	6.52	6.336	6.065	5.862	5.862	5.222	4.885	4.885	4.885	4.885	0.0
Percentage of NoncontrollingInterestInVariableInterestEntity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0

us-gaap:NoncontrollingInterestInVariableInterestEntity us-gaap:ConsolidatedEntities, us-gaap:Ownership

us-gaap:VariableInterestEntityPrimaryBeneficiary, krc:A101FirstLLCand303SecondLLC

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31
Value	187	185	191	194	192	191	189
Percentage of NoncontrollingInterestInVariableInterestEntity	97.1	97.1	97.2	97.2	97.1	97.1	97.0

us-gaap:NoncontrollingInterestInVariableInterestEntity us-gaap:Ownership

krc:RedwoodLLC

Period End	2020-12-31	2019-12-31
Value	5.6	5.8
Percentage of NoncontrollingInterestInVariableInterestEntity	2.8	3.0

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	4.74	5.11	5.11	5.11
Percentage of OperatingLeaseWeightedAverageDiscountRatePercent	100.0	100.0	100.0	100.0

us-gaap:OtherCommitment

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30
Value	1000	456	614	737
Percentage of OtherCommitment	100.0	100.0	100.0	100.0

us-gaap:PartnersCapital dei:LegalEntity

us-gaap:PartnersCapital

krc:KilroyRealtyL.P.

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	5079	4369	4003	3773
Percentage of PartnersCapital	100.0	100.0	100.0	100.0

us-gaap:PartnersCapitalAttributableToNoncontrollingInterest dei:LegalEntity

us-gaap:PartnersCapitalAttributableToNoncontrollingInterest

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	192	190	197	200	203	203	201	199	198	195	197	198	187	186
Percentage of PartnersCapitalAttributableToNoncontrollingInterest	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest dei:LegalEntity

us-gaap:PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2015-12-31
Value	5693	5702	5277	5251	5253	5277	4570	4539	4186	4183	4201	4074	4063	3947	3960	3895	3962	3759	3234
Percentage of PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest dei:LegalEntity, us-gaap:StatementEquityComponents

krc:KilroyRealtyL.P., krc:PartnersCapitalCommonUnit

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2015-12-31
Value	5500	5512	5079	5051	5049	5074	4369	4340	3988	3987	4003	3876	3876	3759	3773	3763	3732	3431	3031
Percentage of PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest	96.6	96.7	96.3	96.2	96.1	96.1	95.6	95.6	95.3	95.3	95.3	95.1	95.4	95.2	95.3	96.6	94.2	91.3	93.7

krc:KilroyRealtyL.P., us-gaap:NoncontrollingInterest

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2015-12-31
Value	192	190	197	200	203	203	201	199	198	195	197	198	187	188	186	132	133	135	10
Percentage of PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest	3.4	3.3	3.7	3.8	3.9	3.9	4.4	4.4	4.7	4.7	4.7	4.9	4.6	4.8	4.7	3.4	3.4	3.6	0.3

us-gaap:PrepaidExpenseAndOtherAssets

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	67	50	53	55	68	67	55	109	55	50	52	72	76	107	114	108	98	77	70	60	58	31	22	23	31	22	20	20	21	21	15	17	16	16	9.949	24	46	21	12	19	25	13	8.097	6.307
Percentage of PrepaidExpenseAndOtherAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PrepaidExpenseAndOtherAssets dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	67	50	53	55	68	67	55	109	55	50	52	72	76	114
Percentage of PrepaidExpenseAndOtherAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PrepaidExpenseCurrentAndNoncurrent

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2015-12-31
Value	26	9.753	10	12	15	31	18	71	17	12	13	33	36	63	55	48	39	18	10	12
Percentage of PrepaidExpenseCurrentAndNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PrepaidExpenseCurrentAndNoncurrent us-gaap:SubsequentEventType

us-gaap:SubsequentEvent

Period End	2021-07-08
Value	5.0
Percentage of PrepaidExpenseCurrentAndNoncurrent	0.0

us-gaap:RealEstateAccumulatedDepreciation

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2015-06-30	2014-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31	2009-12-31	2008-12-31
Value	1798	1561	1391	1264	1139	994	994	947	818	756	742	672	605	532
Percentage of RealEstateAccumulatedDepreciation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31
Value	7686	7104	6326	5649	5280	4620	4018	3623	3048
Percentage of RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateAndAccumulatedDepreciationCarryingAmountOfLand

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31
Value	2503	2524	2100	1768	1780	1437	1245	1134	750
Percentage of RealEstateAndAccumulatedDepreciationCarryingAmountOfLand	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31
Value	5118	4438	3591	2936	2476	1789	1227	913	740
Percentage of RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31
Value	2699	2717	2777	2754	2843	2870	2806	2734	2325
Percentage of RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateAndAccumulatedDepreciationInitialCostOfLand

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31
Value	2371	2472	2058	1726	1740	1397	1231	1109	731
Percentage of RealEstateAndAccumulatedDepreciationInitialCostOfLand	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateGrossAtCarryingValue

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2014-12-31	2013-12-31
Value	10190	9628	8426	7417	7060	6057	5264
Percentage of RealEstateGrossAtCarryingValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateInvestmentPropertyAccumulatedDepreciation

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	1900	1838	1798	1744	1684	1622	1561	1505	1480	1441	1391	1411	1361	1312	1264	1216	1234	1186	1139	1095	1054	1034	994	999	960	921	947	912	885	854	818	781	815	790	756	725	801	770	742	732	720	695	672	605
Percentage of RealEstateInvestmentPropertyAccumulatedDepreciation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateInvestmentPropertyAccumulatedDepreciation dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	1900	1838	1798	1744	1684	1622	1561	1505	1480	1441	1391	1411	1361	1264
Percentage of RealEstateInvestmentPropertyAccumulatedDepreciation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateInvestmentPropertyAtCost

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31	2008-12-31
Value	10552	9792	10190	10086	9945	9822	9628	8977	8824	8616	8426	8329	8138	7645	7417	7239	7276	7159	7060	6632	6553	6498	6328	6354	6109	5985	6057	5751	5667	5434	5264	5048	5096	5016	4757	4399	4271	3993	3798	3748	3652	3266	3216	2520	2475
Percentage of RealEstateInvestmentPropertyAtCost	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateInvestmentPropertyAtCost dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	10552	9792	10190	10086	9945	9822	9628	8977	8824	8616	8426	8329	8138	7417
Percentage of RealEstateInvestmentPropertyAtCost	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateInvestmentPropertyNet

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	8651	7953	8391	8342	8260	8199	8067	7472	7343	7174	7035	6918	6776	6333	6153	6023	6042	5973	5920	5537	5498	5464	5333	5354	5148	5064	5110	4838	4781	4579	4445	4266	4280	4225	4000	3673	3470	3222	3056	3016	2931	2570	2544	1914
Percentage of RealEstateInvestmentPropertyNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RealEstateInvestmentPropertyNet dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	8651	7953	8391	8342	8260	8199	8067	7472	7343	7174	7035	6918	6776	6153
Percentage of RealEstateInvestmentPropertyNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RedeemableNoncontrollingInterestEquityCommonFairValue

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	81	76	65	102	118	114	167	158	153	153	126	143	156	146	154	145	158	150	174	181	168	158	112	118	124	137	126	107	112	105	90	92	94	95	85	84	81	78	64	56	66	61
Percentage of RedeemableNoncontrollingInterestEquityCommonFairValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RestrictedCash us-gaap:DisposalGroupClassification

us-gaap:RestrictedCash

us-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperations

Period End	2021-03-31	2020-12-31	2018-12-31	2017-12-31
Value	1000	74	113	0.0
Percentage of RestrictedCash	100.0	100.0	100.0	0.0

us-gaap:RestrictedCashAndCashEquivalents

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	450	1028	91	16	16	16	16	6.3	6.3	6.3	119	0.0	0.0	0.0	9.149	179	8.249	7.199	56	57	266	261	0.696	8.13	7.462	8.287	75	17	93	33	49	17	19	19	247	5.884	0.097	43	0.358	25	1.349	1.899	1.461	2.059
Percentage of RestrictedCashAndCashEquivalents	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RestrictedCashAndCashEquivalents dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2015-12-31
Value	450	1028	91	16	16	16	16	6.3	6.3	6.3	119	0.0	0.0	0.0	9.149	179	8.249	56	0.696
Percentage of RestrictedCashAndCashEquivalents	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RestrictedCashAndCashEquivalents us-gaap:DisposalGroupClassification

us-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperations

Period End	2021-06-30
Value	431
Percentage of RestrictedCashAndCashEquivalents	95.8

us-gaap:SecuredDebt

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	251	252	253	254	256	257	258	259	259	259	335	336	338	339	340	465	467	469	472	370	373	378	381	475	479	516	546	549	553	556	560	563	569	570	561	520	381	350	351	473	475	446	313	294
Percentage of SecuredDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:SecuredDebt dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	251	252	253	254	256	257	258	259	259	259	335	336	338	340
Percentage of SecuredDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:SecuredDebt dei:LegalEntity, us-gaap:LongtermDebtType

krc:KilroyRealtyL.P., us-gaap:SecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	254	259	336	341
Percentage of SecuredDebt	100.3	100.4	100.3	100.3

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue krc:AwardFeature, us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

krc:NonvestedRestrictedStockUnitsRSU, krc:TimeBasedRestrictedStockUnitsRsus

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31
Value	67.97	66.66	65.87	66.83	59.07
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	100.0	100.0	100.0	100.0	100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue us-gaap:AwardType

krc:MarketMeasureBasedRestrictedStockUnitsRsus

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31
Value	72.06	71.04	67.29	68.83	64.95	67.68	58.77	46.47	41.2
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	106.0	106.6	102.2	103.0	110.0	0.0	0.0	0.0	0.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant

Period End	2021-06-30	2021-03-31	2020-09-30	2013-09-30
Value	1400000.0	1300000.0	1600000.0	28355.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	100.0	100.0	100.0	100.0

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant us-gaap:PlanName

krc:KilroyRealty2006IncentiveAwardPlan

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2013-12-31
Value	1500000.0	400000.0	600000.0	1946600.0	7414.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	0.0	0.0	0.0	0.0	0.0

us-gaap:SharePrice us-gaap:AwardType

us-gaap:SharePrice

krc:A2021PerformanceBasedRSUs

Period End	2021-02-18
Value	57.85
Percentage of SharePrice	100.0

us-gaap:SharesIssuedPricePerShare us-gaap:StatementEquityComponents

us-gaap:SharesIssuedPricePerShare

krc:IssuanceOfEquityUnderAtmProgram

Period End	2020-12-31	2018-12-31	2017-12-31	2016-12-31
Value	80.08	73.64	75.4	71.5
Percentage of SharesIssuedPricePerShare	100.0	100.0	100.0	100.0

us-gaap:TradingSecurities

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	25	24	27	25	23	19	27	26	25	24	21	23	22	21	20	18	16	15	14	14	13	13	12	12	13	13	11	12	11	11	10	9.192	8.286	8.029	7.435	6.812	6.546	6.459	5.691	5.213	5.654	5.425	4.902	3.452
Percentage of TradingSecurities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:TradingSecurities dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	25	24	27	25	23	19	27	26	25	24	21	23	22	20
Percentage of TradingSecurities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:UnamortizedDebtIssuanceExpense dei:LegalEntity

us-gaap:UnamortizedDebtIssuanceExpense

krc:KilroyRealtyL.P.

Period End	2020-12-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30
Value	22	20	21	16	16	17	13	13
Percentage of UnamortizedDebtIssuanceExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:UnamortizedDebtIssuanceExpense dei:LegalEntity, us-gaap:LongtermDebtType

krc:KilroyRealtyL.P., krc:UnsecuredTermLoanFacilityUnsecuredSeniorNotesandSecuredDebt

Period End	2021-06-30	2021-03-31	2020-09-30	2020-06-30	2020-03-31
Value	20	21	23	20	19
Percentage of UnamortizedDebtIssuanceExpense	0.0	0.0	0.0	0.0	0.0

krc:KilroyRealtyL.P., us-gaap:RevolvingCreditFacility

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	8.3	1.7	2.1	2.4	2.7	3.1	3.4	3.7	4.0	4.4	4.7	5.0	5.3	6.0
Percentage of UnamortizedDebtIssuanceExpense	0.0	0.0	9.4	0.0	0.0	0.0	16.7	17.5	24.8	26.3	27.0	37.6	38.7	0.0

krc:KilroyRealtyL.P., us-gaap:SecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	0.783	0.909	1.039	1.175
Percentage of UnamortizedDebtIssuanceExpense	3.5	4.5	6.0	0.0

us-gaap:UnamortizedDebtIssuanceExpense us-gaap:LongtermDebtType

us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	21	18	15	12
Percentage of UnamortizedDebtIssuanceExpense	96.4	92.1	88.5	0.0

us-gaap:UnamortizedDebtIssuanceExpense us-gaap:MortgageLoansOnRealEstateDescriptionTypeOfProperty

srt:OfficeBuilding

Period End	2020-12-31	2019-12-31
Value	0.8	0.9
Percentage of UnamortizedDebtIssuanceExpense	3.6	4.4

us-gaap:UnsecuredDebt

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2009-12-31
Value	3672	3671	3670	3668	3399	3050	3049	3048	2553	2552	2552	2207	2156	2155	2006	1909	2097	2096	1847	1846	1845	1845	1856	2181	1783	1783	1783	1743	1431	1431	1431	1431	1430	1430	1130	1130	1130	1130	980	980	655	655	655	144
Percentage of UnsecuredDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:UnsecuredDebt dei:LegalEntity

krc:KilroyRealtyL.P.

Period End	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	3672	3671	3670	3668	3399	3050	3049	3048	2553	2552	2552	2207	2156	2006
Percentage of UnsecuredDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:UnsecuredDebt dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:LongtermDebtType

krc:KilroyRealtyL.P., krc:A2500UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	418
Percentage of UnsecuredDebt	11.4

krc:KilroyRealtyL.P., krc:A3.050UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31
Value	494	494	0.0
Percentage of UnsecuredDebt	13.5	16.2	0.0

krc:KilroyRealtyL.P., krc:A3.350UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	174	174	174	173
Percentage of UnsecuredDebt	4.7	5.7	6.8	8.7

krc:KilroyRealtyL.P., krc:A3.450UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	422	422	421	420
Percentage of UnsecuredDebt	11.5	13.8	16.5	21.0

krc:KilroyRealtyL.P., krc:A3.450UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	74	74	74	74
Percentage of UnsecuredDebt	2.0	2.4	2.9	3.7

krc:KilroyRealtyL.P., krc:A3.800UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	299	299	298	298
Percentage of UnsecuredDebt	8.2	9.8	11.7	14.9

krc:KilroyRealtyL.P., krc:A4.250UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	395	394	394	393
Percentage of UnsecuredDebt	10.8	13.0	15.5	19.6

krc:KilroyRealtyL.P., krc:A4.300UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	49	49	49	0.0
Percentage of UnsecuredDebt	1.4	1.6	1.9	0.0

krc:KilroyRealtyL.P., krc:A4.350UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	198	198	198	0.0
Percentage of UnsecuredDebt	5.4	6.5	7.8	0.0

krc:KilroyRealtyL.P., krc:A4.375UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	397	396	396	395
Percentage of UnsecuredDebt	10.8	13.0	15.5	19.7

krc:KilroyRealtyL.P., krc:A4.750UnsecuredNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	396	395	395	0.0
Percentage of UnsecuredDebt	10.8	13.0	15.5	0.0

krc:KilroyRealtyL.P., krc:A4270UnsecuredSeniorNotes, us-gaap:UnsecuredDebt

Period End	2020-12-31
Value	348
Percentage of UnsecuredDebt	9.5

us-gaap:UnsecuredDebt dei:LegalEntity, us-gaap:LongtermDebtType

krc:KilroyRealtyL.P., us-gaap:UnsecuredDebt

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31
Value	3670	2899	2402	2006
Percentage of UnsecuredDebt	100.0	95.1	94.2	100.0

us-gaap:ValuationAllowancesAndReservesBalance us-gaap:ValuationAllowancesAndReservesType

us-gaap:ValuationAllowancesAndReservesBalance

krc:AllowanceForDeferredRent

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31
Value	804000.0	1552000.0	3339000.0	3238000.0	1524000.0	1882000.0
Percentage of ValuationAllowancesAndReservesBalance	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AllowanceForLoanAndLeaseLossesRealEstate

Period End	2020-12-31	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31
Value	1799000.0	1171000.0	4639000.0	2309000.0	1712000.0	2080000.0
Percentage of ValuationAllowancesAndReservesBalance	223.8	75.5	138.9	71.3	112.3	110.5

Line plots across dimensions of each concept

us-gaap:AllocatedShareBasedCompensationExpense
us-gaap:AwardType
(None,)

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents
(None,)

us-gaap:FiniteLivedIntangibleAssetsNet
krc:FiniteLivedIntangibleAssetsAndLiabilitiesByMajorClass
(None,)

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
us-gaap:StatementEquityComponents
(None,)

us-gaap:StockIssuedDuringPeriodValueNewIssues
us-gaap:StatementEquityComponents
(None,)

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents
(None,)

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents
(None,)

KRC

Table of contents

Plots across concepts

Tables

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding dei:LegalEntity

krc:KilroyRealtyL.P.

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic dei:LegalEntity

krc:KilroyRealtyL.P.

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic dei:LegalEntity

krc:KilroyRealtyL.P.

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted dei:LegalEntity

krc:KilroyRealtyL.P.

Allocated Share Based Compensation Expense

us-gaap:AllocatedShareBasedCompensationExpense

us-gaap:AllocatedShareBasedCompensationExpense

us-gaap:AllocatedShareBasedCompensationExpense us-gaap:AwardType

krc:A2021PerformanceBasedRSUs

krc:AcceleratedCompensationRelatedtoSeverancePackages

krc:PerformanceBasedRSUs

General And Administrative Expense

us-gaap:GeneralAndAdministrativeExpense

us-gaap:GeneralAndAdministrativeExpense

us-gaap:GeneralAndAdministrativeExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest dei:LegalEntity

krc:KilroyRealtyL.P.

Interest Expense

us-gaap:InterestExpense

us-gaap:InterestExpense

us-gaap:InterestExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Interest Paid Net

us-gaap:InterestPaidNet

us-gaap:InterestPaidNet

us-gaap:InterestPaidNet dei:LegalEntity

krc:KilroyRealtyL.P.

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss dei:LegalEntity

krc:KilroyRealtyL.P.

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest dei:LegalEntity

krc:KilroyRealtyL.P.

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic dei:LegalEntity

krc:KilroyRealtyL.P.

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense

us-gaap:NonoperatingIncomeExpense

us-gaap:NonoperatingIncomeExpense dei:LegalEntity

krc:KilroyRealtyL.P.

Operating Expenses

us-gaap:OperatingExpenses

us-gaap:OperatingExpenses

us-gaap:OperatingExpenses dei:LegalEntity

krc:KilroyRealtyL.P.

Profit Loss