TNK

Line plots across dimensions of each concept
Tables

Table of contents

us-gaap:StatementEquityComponents
us-gaap:SharesOutstanding
us-gaap:StatementClassOfStock
us-gaap:CommonStockSharesIssued
us-gaap:StatementClassOfStock
us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStockSharesAuthorized
us-gaap:StatementClassOfStock

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService

us-gaap:Revenues

us-gaap:CostOfGoodsAndServicesSold
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingCostsAndExpenses
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:RelatedPartyTransaction

us-gaap:GeneralAndAdministrativeExpense
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingIncomeLoss
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:InterestExpense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:IncomeTaxExpenseBenefit

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:Assets
us-gaap:StatementBusinessSegments

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity
us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:AssetsCurrent

us-gaap:CashAndCashEquivalentsAtCarryingValue
us-gaap:LongLivedAssetsHeldForSaleByAssetType

us-gaap:AccountsReceivableNetCurrent

us-gaap:InventoryNet

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

us-gaap:Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill

us-gaap:OtherAssetsNoncurrent

us-gaap:LiabilitiesCurrent

us-gaap:LongTermDebtCurrent

us-gaap:AccountsPayableCurrent

us-gaap:AccruedLiabilitiesCurrent

us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:OtherLiabilitiesCurrent
us-gaap:ProductOrService
us-gaap:ContractWithCustomerLiabilityCurrent

us-gaap:LongTermDebt
us-gaap:DebtInstrument, us-gaap:SubsequentEventType
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:LongTermDebtNoncurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:StockholdersEquity
us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:CommonStocksIncludingAdditionalPaidInCapital

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:UnrecognizedTaxBenefits

us-gaap:OperatingLeaseRightOfUseAsset
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

tnk:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRealizedGainLossNet
us-gaap:DerivativeInstrumentRisk
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities, us-gaap:StatementClassOfStock
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

us-gaap:DepreciationAndAmortization
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
us-gaap:DerivativeInstrumentRisk
us-gaap:IncomeStatementLocation
us-gaap:EmployeeBenefitsAndShareBasedCompensation

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax
us-gaap:PropertyPlantAndEquipmentByType
us-gaap:GainLossOnDispositionOfAssets
us-gaap:SubsequentEventType
us-gaap:GainLossOnSaleOfPropertyPlantEquipment

us-gaap:GainLossOnSalesOfAssetsAndAssetImpairmentCharges
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:IncomeLossFromEquityMethodInvestments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InvestmentIncomeInterest

us-gaap:LeaseAndRentalExpense
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OtherNonoperatingIncome
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:StatementBusinessSegments
us-gaap:ProceedsFromDivestitureOfBusinesses
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:StatementBusinessSegments, us-gaap:SubsequentEventType

us-gaap:RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty
us-gaap:RelatedPartyTransaction
us-gaap:RelatedPartyTransaction
us-gaap:RevenueFromRelatedParties
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesEmployeeBenefitPlan

us-gaap:UnrealizedGainLossOnDerivatives
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis
tnk:AccruedLiabilitiesReceivablesCurrent
us-gaap:FairValueByMeasurementBasis
us-gaap:DebtInstrument
tnk:ActualHullCoverageRatio
us-gaap:PropertyPlantAndEquipmentByType, us-gaap:SaleLeasebackTransactionDescription
us-gaap:SaleLeasebackTransactionDescription
tnk:LeaseObligationType
tnk:DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLine
us-gaap:DebtInstrument
tnk:LeaseObligationType
tnk:DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLineAsPercentageOfDebt
us-gaap:DebtInstrument
us-gaap:DebtInstrument
tnk:DebtInstrumentCollateralNumberofVessels
us-gaap:DebtInstrument, us-gaap:LongtermDebtType, us-gaap:SubsequentEventType
us-gaap:LongtermDebtType

us-gaap:AccruedFeesAndOtherRevenueReceivable

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipmentExcludingCapitalLeasedAssets
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency
us-gaap:AdvancesToAffiliate
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency
us-gaap:AssetsHeldForSaleLongLivedFairValueDisclosure

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent

us-gaap:DebtInstrumentCarryingAmount
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
us-gaap:LongtermDebtType
us-gaap:ShortTermDebtType
us-gaap:DebtInstrumentInterestRateEffectivePercentage

us-gaap:DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet

us-gaap:DerivativeAssetsCurrent
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis
us-gaap:DerivativeAssetsNoncurrent
us-gaap:FairValueByMeasurementBasis

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue

us-gaap:DerivativeLiabilitiesCurrent
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis

us-gaap:DerivativeLiabilitiesNoncurrent
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis

us-gaap:DueFromAffiliateCurrent

us-gaap:DueToAffiliateCurrent
us-gaap:RelatedPartyTransaction

us-gaap:FinanceLeaseLiability
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:FinanceLeaseLiabilityCurrent

us-gaap:FinanceLeaseLiabilityNoncurrent
tnk:LeaseObligationType
us-gaap:FinanceLeaseLiabilityPaymentsDue
tnk:LeaseObligationType
us-gaap:FinanceLeaseLiabilityUndiscountedExcessAmount

us-gaap:FinanceLeaseRightOfUseAsset

us-gaap:FinanceLeaseWeightedAverageDiscountRatePercent

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency
us-gaap:InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency
us-gaap:InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue

us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent
us-gaap:LongtermDebtType
us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity
us-gaap:LongtermDebtType
us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity

us-gaap:LongtermDebtWeightedAverageInterestRate

us-gaap:PrepaidExpenseCurrent

us-gaap:PropertyPlantAndEquipmentNetExcludingCapitalLeasedAssets
us-gaap:LongLivedAssetsHeldForSaleByAssetType
us-gaap:RestrictedCashAndCashEquivalents

us-gaap:RestrictedCashCurrent

us-gaap:RestrictedCashNoncurrent

us-gaap:SaleLeasebackTransactionAccumulatedDepreciation

us-gaap:ShortTermBorrowings
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

Tables

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:CommonStockSharesIssued us-gaap:StatementClassOfStock us-gaap:CommonClassA	▁▁██████▅▅▅▅▅▅	29.1	29.0	232.0	232.0	231.6	231.6	231.6	231.2	142.2	142.2	136.1	133.1	133.1	132.8	NA	103.6	71.2	71.1	NA
us-gaap:CommonStockSharesIssued us-gaap:StatementClassOfStock us-gaap:CommonClassB	▁▁████████▅▅▅▅	4.6	4.6	37.0	37.0	37.0	37.0	37.0	37.0	37.0	37.0	23.2	23.2	23.2	23.2	NA	16.7	12.5	12.5	NA
us-gaap:CommonStockSharesOutstanding us-gaap:StatementClassOfStock us-gaap:CommonClassA	▁▁██████▅▅▅▅▅▅	29.1	29.0	232.0	232.0	231.6	231.6	231.6	231.2	142.2	142.2	136.1	133.1	133.1	132.8	NA	103.6	71.2	71.1	NA
us-gaap:CommonStockSharesOutstanding us-gaap:StatementClassOfStock us-gaap:CommonClassB	▁▁████████▅▅▅▅	4.6	4.6	37.0	37.0	37.0	37.0	37.0	37.0	37.0	37.0	23.2	23.2	23.2	23.2	NA	16.7	12.5	12.5	NA
us-gaap:CommonStockSharesAuthorized	██████▃▃▁▁▁▁▁▁	585.0	585.0	585.0	585.0	585.0	585.0	385.0	385.0	300.0	300.0	300.0	300.0	300.0	300.0	NA	300.0	300.0	300.0	NA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding	▄	33.97873	NA	268.990399	268.990399	NA	268.558556	268.558556	NA	179.224094	169.963717	NA	156.284136	156.446895	NA	135.174756	116.725428	83.966874	83.59103	79.911673
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic	▄	33.727978	NA	268.990399	268.990399	NA	268.558556	268.558556	NA	179.224094	169.963717	NA	156.284136	156.208917	NA	134.630768	116.150985	83.676425	83.59103	79.911673
us-gaap:EarningsPerShareBasic	█▄▁▁▂▁▁▁▁▁▂▁▂▂▂▂▂▁▂	2.91	1.31	-0.07	-0.05	0.03999999999999998	-0.07	-0.1	0.0	-0.12	-0.22	0.040000000000000036	-0.03	0.14	0.3400000000000001	0.31	0.38	0.05	-0.07	0.01
us-gaap:EarningsPerShareDiluted	█▄▁▁▂▁▁▁▁▁▂▁▂▂▂▂▂▁▂	2.89	1.31	-0.07	-0.05	0.03999999999999998	-0.07	-0.1	0.0	-0.12	-0.22	0.040000000000000036	-0.03	0.14	0.33000000000000007	0.3	0.38	0.05	-0.07	0.01

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax	▆█▄▅▆▄▄▂▂▃▃▃▃▄▃▃▁▁▁	246.492	326.835	182.304	202.277	239.724	175.915	171.659	100.666	91.238	108.789	141.351	104.621	139.621	168.986	126.401	107.594	44.433	43.492	51.04
us-gaap:Revenues	▆█▄▅▆▄▄▂▂▃▃▃▃▄▃▃▁▁▁	246.492	326.835	182.304	202.277	239.724	175.915	171.659	100.666	91.238	108.789	117.704	104.621	139.621	168.986	126.401	107.594	44.433	43.492	51.04
us-gaap:CostOfGoodsAndServicesSold	▄█▆▆▇▅▆▁▁▁	61.558	124.561	87.726	92.668	110.602	83.048	86.933	15.88	18.303	19.43	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:OperatingCostsAndExpenses	▄	46.218	NA	NA	53.6	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:GeneralAndAdministrativeExpense	▇▇▇▇█▇▇▇▇▇▁▇▇	9.784	8.992	8.739	9.508	11.836	8.747	9.407	8.004	7.622	8.365	-8.977	8.214	9.503	NA	NA	3.039	3.163	3.362	2.322
us-gaap:OperatingIncomeLoss	██▂▂▄▂▁▂▁▂▂▂▄▆▅▅▃▂▂	92.986	91.608	-4.873	5.051	31.206	-2.166	-13.415	2.822	-13.734	1.587	5.66	-3.793	30.751	56.53	44.584	43.668	10.491	-5.534	6.918
us-gaap:InterestExpense	▆▇███▇▇▄▃▃▃▃▃▄▂▁▁▁▃	13.492	15.679	16.134	16.607	16.987	15.006	13.931	9.613	7.299	7.076	7.363	6.809	7.341	7.73	4.008	3.075	2.274	2.604	6.654
us-gaap:OtherNonoperatingIncomeExpense	▄▃▄▃█▂▂▄▂▁▂▃▂▂▂▃▃▃▂	940000.0	-487000.0	933000.0	614000.0	7122000.0	-799000.0	-1273000.0	917000.0	-1768000.0	-2761000.0	-1938000.0	453000.0	-1940000.0	-1259000.0	-1385000.0	-474000.0	-89000.0	-354000.0	-703000.0
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	▄	83.6	NA	NA	-12.668	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:IncomeTaxExpenseBenefit	▄	-14.598	NA	NA	1.639	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:ProfitLoss	█▆▂▂▄▂▂▃▂▁▃▃▄▆▅▅▃▃▃	98.198	63.072	-19.85	-14.307	11.502	-17.484	-27.413	-1.879	-22.38	-37.477	6.846	-5.457	22.486	53.559	40.95	44.242	4.589	-5.724	-4.323

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
COGS Ratio us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,tnk:Tankers	▄	245728000.0	NA	NA	197442000.0	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Operating Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,tnk:ShipToShipTransfer	▁▆▅▅▇▇▆▆▇█▆▆▆▆▅	764000.0	10220000.0	8685000.0	9565000.0	13114000.0	12019000.0	11210000.0	11035000.0	11902000.0	14597000.0	10214000.0	9837000.0	10999000.0	9737000.0	8850000.0	NA	NA	NA	NA
Operating Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,tnk:Tankers	▄	245728000.0	NA	NA	197442000.0	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:Assets	▆█▇▇▇▇▇█▁▂▄▄▆▇	2071.966	2229.476	2170.138	2153.928	2161.086	2129.194	2140.696	2197.348	1735.953	1803.426	1932.425	1957.784	2063.73	2169.476	NA	1314.155	977.499	1091.833	NA
us-gaap:Liabilities	▁▇▇▇▇▆▆▆▁▂▃▄▅█	876.167	1239.556	1243.851	1208.033	1214.153	1193.983	1188.226	1190.747	873.525	913.457	1011.801	1047.11	1138.413	1292.015	NA	731.333	664.808	802.158	NA
us-gaap:LiabilitiesAndStockholdersEquity	▆█▇▇▇▇▇█▁▂▄▄▆▇	2071.966	2229.476	2170.138	2153.928	2161.086	2129.194	2140.696	2197.348	1735.953	1803.426	1932.425	1957.784	2063.73	2169.476	NA	1314.155	977.499	1091.833	NA
us-gaap:StockholdersEquity	█▄▂▃▃▃▃▄▁▂▂▂▂▁	1195.799	989.92	926.287	945.895	946.933	935.211	952.47	1006.601	862.428	889.969	920.624	910.674	925.317	877.461	NA	582.822	312.691	289.675	NA

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:AssetsCurrent	▆█▄▃▃▂▁▂▁▂▃▂▄▄	348.917	421.225	261.544	228.478	225.591	177.799	168.329	176.685	149.187	178.992	215.484	186.814	251.181	279.814	NA	191.76	83.241	204.721	NA
us-gaap:CashAndCashEquivalentsAtCarryingValue	█▄▄▂▃▃▂▃▃▄▃▃▃▅▄▄▁▂▁	167.907	88.824	76.705	35.429	54.917	54.361	48.457	71.439	60.606	87.255	68.108	59.237	58.018	96.417	80.579	83.082	21.764	37.708	18.554
us-gaap:AccountsReceivableNetCurrent	▇█▄▄▁▁▁▁▂▁▂▂▃▂	88.663	95.648	52.245	51.451	17.365	17.048	15.912	19.288	22.484	18.187	30.247	25.245	43.611	28.313	NA	11.344	2.545	7.633	NA
us-gaap:InventoryNet	▂▆▆█▁	30.885	49.79	50.473	63.441	23.179	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:PropertyPlantAndEquipmentNet	▆▇██▂▄▆▆▁▄▅▆▆▇	1683.734	1769.726	1859.733	1875.855	1401.551	1556.959	1695.722	1737.792	1283.989	1554.055	1605.372	1664.859	1706.288	1767.925	NA	1035.311	841.013	867.035	NA
us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures	▂▁▁▁▁▁▁▁▃▃▇▇▇█	29.74	28.112	26.418	26.351	25.766	24.811	25.17	25.46	42.927	43.201	81.273	78.771	77.862	86.808	NA	79.566	NA	7.289	NA
us-gaap:Goodwill	▃▃███████████▁	2.426	2.426	8.059	8.059	8.059	8.059	8.059	8.059	8.059	8.059	8.059	8.059	8.059	0.0	NA	NA	NA	NA	NA
us-gaap:IntangibleAssetsNetExcludingGoodwill	▁▁▃▃▃▄▄▄▄▅▅▅▅█	2.259	2.545	9.955	10.498	11.625	12.32	13.03	14.605	15.262	16.044	17.658	18.491	19.342	29.619	NA	NA	NA	NA	NA
us-gaap:OtherAssetsNoncurrent	▆█▄▅▁▁▁▁▁▁▁▁▁▁	1453000.0	1923000.0	910000.0	1010000.0	74000.0	82000.0	92000.0	127000.0	139000.0	155000.0	41000.0	73000.0	82000.0	146000.0	NA	1992000.0	4564000.0	2958000.0	NA

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:LiabilitiesCurrent	▁▇█▆▂▁▅▄▄▄▄▄▄█	185.818	279.705	295.414	269.501	197.761	179.231	241.927	236.714	223.623	224.096	236.922	222.093	228.798	289.652	NA	187.787	86.507	72.748	NA
us-gaap:LongTermDebtCurrent	▁▂▅▅▅▅▇█▇▇█▇▇█	27.549	43.573	101.295	101.264	106.236	103.843	155.089	166.745	159.087	150.254	171.019	155.69	151.761	174.047	NA	144.453	51.959	25.246	NA
us-gaap:AccountsPayableCurrent	▇█▆▅▂▁▁▁▂▁▂▁▂▂	59.652	70.978	54.824	47.532	11.146	5.352	5.822	7.86	10.353	9.253	12.265	9.858	10.784	16.717	NA	5.747	3.388	2.098	NA
us-gaap:AccruedLiabilitiesCurrent	▄█▅▇▄▃▃▃▂▁▁▁▅█	40.36	59.735	46.519	56.448	40.856	35.717	34.063	34.608	29.756	26.157	27.224	26.259	47.121	62.029	NA	18.218	14.971	14.543	NA
us-gaap:OperatingLeaseLiabilityCurrent	▆██▆▁	10.986	16.29	16.405	12.224	0.0	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:OtherLiabilitiesCurrent	██▁▁▁	8485000.0	8567000.0	255000.0	316000.0	0.0	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:ContractWithCustomerLiabilityCurrent us-gaap:ProductOrService tnk:Timecharter	█▁	7700000.0	7500000.0	NA	NA	0.0	100000.0	0.0	500000.0	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:LongTermDebt	▁▃▃▃▄▅▆▆▄▅▆▆▇█	312.938	559.679	608.96	593.226	735.406	807.078	933.817	952.302	645.905	821.786	933.016	966.651	1044.27	1164.605	NA	674.672	609.398	730.214	NA
us-gaap:LongTermDebtNoncurrent	▁▃▃▃▄▅▆▆▃▅▆▆▇█	285.389	516.106	507.665	491.962	629.17	703.235	778.728	785.557	486.818	671.532	761.997	810.961	892.509	990.558	NA	530.219	557.439	704.968	NA
us-gaap:OtherLiabilitiesNoncurrent	▄█▅▅▅▄▄▃▂▂▁	27.516	51.044	37.474	37.166	32.829	30.646	29.62	26.795	19.226	17.829	13.683	NA	NA	NA	NA	NA	5.444	4.902	NA
us-gaap:OperatingLeaseLiabilityNoncurrent	▁▄██▁	417000.0	3270000.0	7190000.0	6865000.0	0.0	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:StockholdersEquity	█▄▂▃▃▃▃▄▁▂▂▂▂▁	1195.799	989.92	926.287	945.895	946.933	935.211	952.47	1006.601	862.428	889.969	920.624	910.674	925.317	877.461	NA	582.822	312.691	289.675	NA
us-gaap:CommonStocksIncludingAdditionalPaidInCapital	████████▃▃▁▁▁▁	1298.397	1297.555	1296.993	1296.751	1295.929	1295.709	1295.485	1294.998	1143.569	1143.353	1103.304	1095.511	1095.322	1094.874	NA	853.671	673.966	672.744	NA
us-gaap:RetainedEarningsAccumulatedDeficit	█▃▁▂▂▁▂▃▃▄▆▆▆▅	-102598000.0	-307635000.0	-370706000.0	-350856000.0	-348996000.0	-360498000.0	-343015000.0	-288397000.0	-281141000.0	-253384000.0	-182680000.0	-184837000.0	-170005000.0	-217413000.0	NA	-270849000.0	-361275000.0	-383069000.0	NA
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	▄	374000.0	NA	242000.0	154000.0	235000.0	224000.0	148000.0	167000.0	216000.0	NA	235000.0	189000.0	NA	NA	NA	NA	NA	NA	NA
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap:StatementClassOfStock,us-gaap:StatementEquityComponents us-gaap:CommonClassA,us-gaap:CommonStockIncludingAdditionalPaidInCapital	▄	374000.0	NA	242000.0	154000.0	235000.0	224000.0	148000.0	167000.0	216000.0	NA	235000.0	189000.0	NA	NA	NA	NA	NA	NA	NA

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
us-gaap:ProfitLoss	█▆▂▂▄▂▂▃▂▁▃▃▄▆▅▅▃▃▃	98.198	63.072	-19.85	-14.307	11.502	-17.484	-27.413	-1.879	-22.38	-37.477	6.846	-5.457	22.486	53.559	40.95	44.242	4.589	-5.724	-4.323

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30

		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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30

us-gaap:StatementEquityComponents

us-gaap:SharesOutstanding

us-gaap:CommonStockIncludingAdditionalPaidInCapital

Period End	2020-06-30	2020-03-31	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31	2011-12-31
Value	-33738000.0	33712000.0	33655000.0	268559000.0	268559000.0	268559000.0	268202000.0	179224000.0	179224000.0	159304000.0	156284000.0	156284.0	156031.0	120340.0	112064000.0	83676000.0	83591000.0	83591000.0	61877000.0
Percentage of SharesOutstanding	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Shares Outstanding

us-gaap:StatementClassOfStock

us-gaap:CommonStockSharesIssued

us-gaap:CommonClassA

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	29100000.0	29000000.0	232000000.0	232000000.0	231600000.0	231600000.0	231600000.0	231200000.0	142200000.0	142200000.0	136100000.0	133100000.0	133100000.0	132800000.0	103600000.0	95300000.0	71200000.0	71100000.0	71100000.0	71100000.0	49400000.0	39500000.0
Percentage of CommonStockSharesIssued	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:CommonClassB

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	4600000.0	4600000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	23200000.0	23200000.0	23200000.0	23200000.0	16700000.0	16700000.0	12500000.0	12500000.0	12500000.0	12500000.0	12500000.0	12500000.0
Percentage of CommonStockSharesIssued	15.8	15.9	15.9	15.9	16.0	16.0	16.0	16.0	26.0	26.0	17.0	17.4	17.4	17.5	16.1	17.5	17.6	17.6	17.6	17.6	25.3	31.6

Common Stock Shares Issued

us-gaap:StatementClassOfStock

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonClassA

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	29100000.0	29000000.0	232000000.0	232000000.0	231600000.0	231600000.0	231600000.0	231200000.0	142200000.0	142200000.0	136100000.0	133100000.0	133100000.0	132800000.0	103600000.0	95300000.0	71200000.0	71100000.0	71100000.0	71100000.0	49400000.0	39500000.0
Percentage of CommonStockSharesOutstanding	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:CommonClassB

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	4600000.0	4600000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	37000000.0	23200000.0	23200000.0	23200000.0	23200000.0	16700000.0	16700000.0	12500000.0	12500000.0	12500000.0	12500000.0	12500000.0	12500000.0
Percentage of CommonStockSharesOutstanding	15.8	15.9	15.9	15.9	16.0	16.0	16.0	16.0	26.0	26.0	17.0	17.4	17.4	17.5	16.1	17.5	17.6	17.6	17.6	17.6	25.3	31.6

Common Stock Shares Outstanding

us-gaap:CommonStockSharesAuthorized

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	585000000.0	585000000.0	585000000.0	585000000.0	585000000.0	585000000.0	385000000.0	385000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0	300000000.0
Percentage of CommonStockSharesAuthorized	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:StatementClassOfStock

us-gaap:CommonClassA

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31
Value	485000000.0	485000000.0	485000000.0	485000000.0	485000000.0	485000000.0	285000000.0	285000000.0	200000000.0	200000000.0	200000000.0	200000000.0	200000000.0	200000000.0	200000000.0	200000000.0	200000000.0	200000000.0	200000000.0
Percentage of CommonStockSharesAuthorized	82.9	82.9	82.9	82.9	82.9	82.9	74.0	74.0	66.7	66.7	66.7	66.7	66.7	66.7	66.7	66.7	66.7	66.7	66.7

Common Stock Shares Authorized

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

Period End	2020-06-30	2019-09-30	2019-06-30	2018-09-30	2018-06-30	2017-09-30	2017-06-30	2016-09-30	2016-06-30	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	33978730.0	268990399.0	268990399.0	268558556.0	268558556.0	179224094.0	169963717.0	156284136.0	156446895.0	135174756.0	116725428.0	83966874.0	83591030.0	79911673.0
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

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

Period End	2020-06-30	2019-09-30	2019-06-30	2018-09-30	2018-06-30	2017-09-30	2017-06-30	2016-09-30	2016-06-30	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	33727978.0	268990399.0	268990399.0	268558556.0	268558556.0	179224094.0	169963717.0	156284136.0	156208917.0	134630768.0	116150985.0	83676425.0	83591030.0	79911673.0
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

Weighted Average Number Of Shares Outstanding Basic

us-gaap:EarningsPerShareBasic

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	2.91	1.31	-0.07	-0.05	0.03999999999999998	-0.07	-0.1	0.0	-0.12	-0.22	0.040000000000000036	-0.03	0.14	0.3400000000000001	0.31	0.38	0.05	-0.07	0.01
Percentage of EarningsPerShareBasic	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	100.0	100.0	100.0	100.0	100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareDiluted

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	2.89	1.31	-0.07	-0.05	0.03999999999999998	-0.07	-0.1	0.0	-0.12	-0.22	0.040000000000000036	-0.03	0.14	0.33000000000000007	0.3	0.38	0.05	-0.07	0.01
Percentage of EarningsPerShareDiluted	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	100.0	100.0	100.0	100.0	100.0

Earnings Per Share Diluted

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	246492000.0	326835000.0	182304000.0	202277000.0	239724000.0	175915000.0	171659000.0	100666000.0	91238000.0	108789000.0	141351000.0	104621000.0	139621000.0	168986000.0	126401000.0	107594000.0	44433000.0	43492000.0	51040000.0
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	100.0
Percentage of Revenues	100.0	0.0	100.0	100.0	0.0	100.0	100.0	0.0	100.0	100.0	0.0	100.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:ShipToShipTransfer

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30
Value	764000.0	10220000.0	8685000.0	9565000.0	13114000.0	12019000.0	11210000.0	11035000.0	11902000.0	14597000.0	10214000.0	9837000.0	10999000.0	9737000.0	8850000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	0.3	3.1	4.8	4.7	5.5	6.8	6.5	11.0	13.0	13.4	7.2	9.4	7.9	5.8	7.0
Percentage of Revenues	0.3	0.0	4.8	4.7	0.0	6.8	6.5	0.0	13.0	13.4	0.0	9.4	7.9	0.0	7.0
Percentage of Revenues us-gaap:OperatingSegments tnk:ShipToShipTransfer	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	100.0	100.0	0.0	100.0	100.0	0.0	100.0

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	245728000.0	197442000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	99.7	97.6
Percentage of Revenues	99.7	97.6
Percentage of Revenues us-gaap:OperatingSegments tnk:Tankers	0.0	0.0

us-gaap:ProductOrService

tnk:LNGterminalmanagementconsultancyandotherOtherrevenue

Period End	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	609000.0	2321000.0	819000.0	3704000.0	3627000.0	1275000.0	907000.0	2650000.0	1822000.0	827000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	0.2	0.7	0.4	1.8	1.5	0.7	0.5	2.6	2.0	0.8
Percentage of Revenues	0.2	0.0	0.4	1.8	0.0	0.7	0.5	0.0	2.0	0.8
Percentage of Revenues tnk:LNGterminalmanagementconsultancyandotherOtherrevenue	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:Otherrevenue

Period End	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	3580000.0	10768000.0	7361000.0	14016000.0	12387000.0	11542000.0	9947000.0	11374000.0	12914000.0	15458000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	1.5	3.3	4.0	6.9	5.2	6.6	5.8	11.3	14.2	14.2
Percentage of Revenues	1.5	0.0	4.0	6.9	0.0	6.6	5.8	0.0	14.2	14.2
Percentage of Revenues tnk:Otherrevenue	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:ShiptoshipsupportservicesOtherrevenue

Period End	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	1123000.0	6205000.0	4649000.0	8222000.0	6177000.0	8217000.0	6902000.0	5226000.0	7980000.0	11947000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	0.5	1.9	2.6	4.1	2.6	4.7	4.0	5.2	8.7	11.0
Percentage of Revenues	0.5	0.0	2.6	4.1	0.0	4.7	4.0	0.0	8.7	11.0
Percentage of Revenues tnk:ShiptoshipsupportservicesOtherrevenue	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:TimeChartersAframax

Period End	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	2158000.0	0.0	0.0	0.0	3923000.0	7784000.0	11021000.0	13989000.0	12318000.0	12451000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	0.9	0.0	0.0	0.0	1.6	4.4	6.4	13.9	13.5	11.4
Percentage of Revenues	0.9	0.0	0.0	0.0	0.0	4.4	6.4	0.0	13.5	11.4
Percentage of Revenues tnk:TimeChartersAframax	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:TimeChartersLR2

Period End	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	1828000.0	0.0	0.0	0.0	208000.0	1633000.0	2406000.0	3182000.0	3196000.0	3520000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	0.7	0.0	0.0	0.0	0.1	0.9	1.4	3.2	3.5	3.2
Percentage of Revenues	0.7	0.0	0.0	0.0	0.0	0.9	1.4	0.0	3.5	3.2
Percentage of Revenues tnk:TimeChartersLR2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:TimeChartersSuezmax

Period End	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	31000000.0	10720000.0	1909000.0	1496000.0	3835000.0	2909000.0	3957000.0	9827000.0	9167000.0	14120000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	12.6	3.3	1.0	0.7	1.6	1.7	2.3	9.8	10.0	13.0
Percentage of Revenues	12.6	0.0	1.0	0.7	0.0	1.7	2.3	0.0	10.0	13.0
Percentage of Revenues tnk:TimeChartersSuezmax	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:Timecharter

Period End	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	34986000.0	10720000.0	1909000.0	1496000.0	7966000.0	12326000.0	17384000.0	26998000.0	24681000.0	30091000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	14.2	3.3	1.0	0.7	3.3	7.0	10.1	26.8	27.1	27.7
Percentage of Revenues	14.2	0.0	1.0	0.7	0.0	7.0	10.1	0.0	27.1	27.7
Percentage of Revenues tnk:Timecharter	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:VesselmanagementOtherrevenue

Period End	2020-06-30	2019-06-30
Value	1848000.0	2090000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	0.7	1.0
Percentage of Revenues	0.7	1.0
Percentage of Revenues tnk:VesselmanagementOtherrevenue	0.0	0.0

tnk:VoyageChartersAframax

Period End	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	59369000.0	91321000.0	51075000.0	48889000.0	42878000.0	29210000.0	24265000.0	12350000.0	4869000.0	6056000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	24.1	27.9	28.0	24.2	17.9	16.6	14.1	12.3	5.3	5.6
Percentage of Revenues	24.1	0.0	28.0	24.2	0.0	16.6	14.1	0.0	5.3	5.6
Percentage of Revenues tnk:VoyageChartersAframax	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:VoyageChartersFullServiceLightering

Period End	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	26699000.0	22935000.0	12447000.0	29280000.0	33888000.0	15858000.0	27363000.0	24752000.0	20257000.0	20634000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	10.8	7.0	6.8	14.5	14.1	9.0	15.9	24.6	22.2	19.0
Percentage of Revenues	10.8	0.0	6.8	14.5	0.0	9.0	15.9	0.0	22.2	19.0
Percentage of Revenues tnk:VoyageChartersFullServiceLightering	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:VoyageChartersLR2

Period End	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	27873000.0	35485000.0	23989000.0	26325000.0	26933000.0	16712000.0	11979000.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	11.3	10.9	13.2	13.0	11.2	9.5	7.0	0.0	0.0	0.0
Percentage of Revenues	11.3	0.0	13.2	13.0	0.0	9.5	7.0	0.0	0.0	0.0
Percentage of Revenues tnk:VoyageChartersLR2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:VoyageChartersSuezmax

Period End	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	93985000.0	155606000.0	85523000.0	87001000.0	115672000.0	90267000.0	80721000.0	-6209000.0	271000.0	3450000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	38.1	47.6	46.9	43.0	48.3	51.3	47.0	-6.2	0.3	3.2
Percentage of Revenues	38.1	0.0	46.9	43.0	0.0	51.3	47.0	0.0	0.3	3.2
Percentage of Revenues tnk:VoyageChartersSuezmax	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

tnk:Voyagecharters

Period End	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	207926000.0	305347000.0	173034000.0	191495000.0	219371000.0	152047000.0	144328000.0	30893000.0	25397000.0	30140000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax	84.4	93.4	94.9	94.7	91.5	86.4	84.1	30.7	27.8	27.7
Percentage of Revenues	84.4	0.0	94.9	94.7	0.0	86.4	84.1	0.0	27.8	27.7
Percentage of Revenues tnk:Voyagecharters	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:Revenues

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	246492000.0	326835000.0	182304000.0	202277000.0	239724000.0	175915000.0	171659000.0	100666000.0	91238000.0	108789000.0	117704000.0	104621000.0	139621000.0	168986000.0	126401000.0	107594000.0	44433000.0	43492000.0	51040000.0
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	100.0
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	100.0

Revenues

us-gaap:CostOfGoodsAndServicesSold

Period End	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	61558000.0	124561000.0	87726000.0	92668000.0	110602000.0	83048000.0	86933000.0	15880000.0	18303000.0	19430000.0
Percentage of CostOfGoodsAndServicesSold	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Revenues	25.0	38.1	48.1	45.8	46.1	47.2	50.6	15.8	20.1	17.9

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	61558000.0	97398000.0
Percentage of CostOfGoodsAndServicesSold	100.0	105.1
Percentage of Revenues	25.0	48.2
Percentage of Revenues us-gaap:OperatingSegments tnk:Tankers	0.0	0.0

Cost Of Goods And Services Sold

us-gaap:OperatingCostsAndExpenses

Period End	2020-06-30	2019-06-30
Value	46218000.0	53600000.0
Percentage of OperatingCostsAndExpenses	100.0	100.0
Percentage of Revenues	18.8	26.5

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:ShipToShipTransfer

Period End	2020-06-30	2019-06-30
Value	1078000.0	7419000.0
Percentage of OperatingCostsAndExpenses	2.3	13.8
Percentage of Revenues	0.4	3.7
Percentage of Revenues us-gaap:OperatingSegments tnk:ShipToShipTransfer	0.0	0.0

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	45140000.0	46181000.0
Percentage of OperatingCostsAndExpenses	97.7	86.2
Percentage of Revenues	18.3	22.8
Percentage of Revenues us-gaap:OperatingSegments tnk:Tankers	0.0	0.0

us-gaap:RelatedPartyTransaction

tnk:TechnicalManagementFee

Period End	2020-06-30	2019-06-30
Value	248000.0	0.0
Percentage of OperatingCostsAndExpenses	0.5	0.0
Percentage of Revenues	0.1	0.0
Percentage of Revenues tnk:TechnicalManagementFee	0.0	0.0

Operating Costs And Expenses

us-gaap:GeneralAndAdministrativeExpense

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	9784000.0	8992000.0	8739000.0	9508000.0	11836000.0	8747000.0	9407000.0	8004000.0	7622000.0	8365000.0	-8977000.0	8214000.0	9503000.0	3039000.0	3163000.0	3362000.0	2322000.0
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 Revenues	4.0	2.8	4.8	4.7	4.9	5.0	5.5	8.0	8.4	7.7	-7.6	7.9	6.8	2.8	7.1	7.7	4.5

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:ShipToShipTransfer

Period End	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	2016-12-31	2016-09-30	2016-06-30
Value	147000.0	1084000.0	784000.0	392000.0	740000.0	762000.0	974000.0	723000.0	799000.0	852000.0	1352000.0	617000.0	1136000.0
Percentage of GeneralAndAdministrativeExpense	1.5	12.1	9.0	4.1	6.3	8.7	10.4	9.0	10.5	10.2	-15.1	7.5	12.0
Percentage of Revenues	0.1	0.3	0.4	0.2	0.3	0.4	0.6	0.7	0.9	0.8	1.1	0.6	0.8
Percentage of Revenues us-gaap:OperatingSegments tnk:ShipToShipTransfer	0.0	0.0	0.0	0.0	0.0	0.0	0.0	6.6	6.7	5.8	13.2	6.3	10.3

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	9637000.0	9116000.0
Percentage of GeneralAndAdministrativeExpense	98.5	95.9
Percentage of Revenues	3.9	4.5
Percentage of Revenues us-gaap:OperatingSegments tnk:Tankers	0.0	0.0

General And Administrative Expense

us-gaap:OperatingIncomeLoss

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	92986000.0	91608000.0	-4873000.0	5051000.0	31206000.0	-2166000.0	-13415000.0	2822000.0	-13734000.0	1587000.0	5660000.0	-3793000.0	30751000.0	56530000.0	44584000.0	43668000.0	10491000.0	-5534000.0	6918000.0
Percentage of OperatingIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 Revenues	37.7	28.0	-2.7	2.5	13.0	-1.2	-7.8	2.8	-15.1	1.5	4.8	-3.6	22.0	33.5	35.3	40.6	23.6	-12.7	13.6

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:ShipToShipTransfer

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30
Value	2499000.0	-6000.0	-1013000.0	1021000.0	788000.0	-130000.0	-1041000.0	-461000.0	-49000.0	-1142000.0	-1766000.0	111000.0	-740000.0	-516000.0	322000.0
Percentage of OperatingIncomeLoss	2.7	-0.0	20.8	20.2	2.5	6.0	7.8	-16.3	0.4	-72.0	-31.2	-2.9	-2.4	-0.9	0.7
Percentage of Revenues	1.0	-0.0	-0.6	0.5	0.3	-0.1	-0.6	-0.5	-0.1	-1.0	-1.5	0.1	-0.5	-0.3	0.3
Percentage of Revenues us-gaap:OperatingSegments tnk:ShipToShipTransfer	0.0	0.0	0.0	0.0	0.0	0.0	0.0	-4.2	-0.4	-7.8	-17.3	1.1	-6.7	-5.3	3.6

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	90487000.0	4030000.0
Percentage of OperatingIncomeLoss	97.3	79.8
Percentage of Revenues	36.7	2.0
Percentage of Revenues us-gaap:OperatingSegments tnk:Tankers	0.0	0.0

Operating Income Loss

us-gaap:InterestExpense

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	13492000.0	15679000.0	16134000.0	16607000.0	16987000.0	15006000.0	13931000.0	9613000.0	7299000.0	7076000.0	7363000.0	6809000.0	7341000.0	7730000.0	4008000.0	3075000.0	2274000.0	2604000.0	6654000.0
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
Percentage of Revenues	5.5	4.8	8.9	8.2	7.1	8.5	8.1	9.5	8.0	6.5	6.3	6.5	5.3	4.6	3.2	2.9	5.1	6.0	13.0

Interest Expense

us-gaap:OtherNonoperatingIncomeExpense

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	940000.0	-487000.0	933000.0	614000.0	7122000.0	-799000.0	-1273000.0	917000.0	-1768000.0	-2761000.0	-1938000.0	453000.0	-1940000.0	-1259000.0	-1385000.0	-474000.0	-89000.0	-354000.0	-703000.0
Percentage of OtherNonoperatingIncomeExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 Revenues	0.4	-0.1	0.5	0.3	3.0	-0.5	-0.7	0.9	-1.9	-2.5	-1.6	0.4	-1.4	-0.7	-1.1	-0.4	-0.2	-0.8	-1.4

Other Nonoperating Income Expense

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

Period End	2020-06-30	2019-06-30
Value	83600000.0	-12668000.0
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	100.0	100.0
Percentage of Revenues	33.9	-6.3

Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest

us-gaap:IncomeTaxExpenseBenefit

Period End	2020-06-30	2019-06-30
Value	-14598000.0	1639000.0
Percentage of IncomeTaxExpenseBenefit	100.0	100.0
Percentage of Revenues	-5.9	0.8

Income Tax Expense Benefit

us-gaap:ProfitLoss

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	98198000.0	106839000.0	63072000.0	-19850000.0	-14307000.0	12447000.0	11502000.0	-17484000.0	-27413000.0	-19153000.0	-1879000.0	-22380000.0	-37477000.0	6846000.0	-5457000.0	22486000.0	53559000.0	40950000.0	44242000.0	4589000.0	-5724000.0	-4323000.0
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
Percentage of Revenues	39.8	0.0	19.3	-10.9	-7.1	0.0	4.8	-9.9	-16.0	0.0	-1.9	-24.5	-34.4	5.8	-5.2	16.1	31.7	32.4	41.1	10.3	-13.2	-8.5

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	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	2016-12-31	2016-09-30
Value	98198000.0	106839000.0	-19850000.0	-14307000.0	12447000.0	11502000.0	-17484000.0	-27413000.0	-19153000.0	-1879000.0	-22380000.0	6846000.0	-5457000.0
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
Percentage of Revenues	39.8	0.0	-10.9	-7.1	0.0	4.8	-9.9	-16.0	0.0	-1.9	-24.5	5.8	-5.2
Percentage of Revenues us-gaap:RetainedEarnings	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Profit Loss

us-gaap:Assets

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	2071966000.0	2229476000.0	2170138000.0	2153928000.0	2161086000.0	2129194000.0	2140696000.0	2197348000.0	1735953000.0	1803426000.0	1932425000.0	1957784000.0	2063730000.0	2169476000.0	1314155000.0	1165359000.0	977499000.0	1097529000.0	1091833000.0	1105656000.0	881926000.0	936517000.0
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
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

us-gaap:StatementBusinessSegments

tnk:ShipToShipTransfer

Period End	2020-06-30	2019-12-31	2019-09-30	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2016-09-30	2016-06-30	2015-12-31
Value	0.0	33709000.0	33560000.0	36315000.0	38135000.0	35558000.0	36810000.0	39663000.0	40947000.0	26468000.0	30499000.0	29950000.0	74381000.0
Percentage of Assets	0.0	1.5	1.5	1.7	1.8	1.7	1.7	2.3	2.3	1.4	1.6	1.5	3.4
Percentage of Assets	0.0	1.5	1.5	1.7	1.8	1.7	1.7	2.3	2.3	1.4	1.6	1.5	3.4
Percentage of Assets tnk:ShipToShipTransfer	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

tnk:Tankers

Period End	2020-06-30	2019-12-31	2018-12-31
Value	1904059000.0	2106943000.0	2069854000.0
Percentage of Assets	91.9	94.5	95.8
Percentage of Assets	91.9	94.5	95.8
Percentage of Assets tnk:Tankers	100.0	100.0	100.0

Assets

us-gaap:Liabilities

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	876167000.0	1239556000.0	1243851000.0	1208033000.0	1214153000.0	1193983000.0	1188226000.0	1190747000.0	873525000.0	913457000.0	1011801000.0	1047110000.0	1138413000.0	1292015000.0	731333000.0	709636000.0	664808000.0	812857000.0	802158000.0	803473000.0	392555000.0	493828000.0
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
Percentage of Assets	42.3	55.6	57.3	56.1	56.2	56.1	55.5	54.2	50.3	50.7	52.4	53.5	55.2	59.6	55.7	60.9	68.0	74.1	73.5	72.7	44.5	52.7

Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	2071966000.0	2229476000.0	2170138000.0	2153928000.0	2161086000.0	2129194000.0	2140696000.0	2197348000.0	1735953000.0	1803426000.0	1932425000.0	1957784000.0	2063730000.0	2169476000.0	1314155000.0	1165359000.0	977499000.0	1097529000.0	1091833000.0	1105656000.0	881926000.0	936517000.0
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
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

Liabilities And Stockholders Equity

us-gaap:StockholdersEquity

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	1195799000.0	1097227000.0	989920000.0	926287000.0	945895000.0	960048000.0	946933000.0	935211000.0	952470000.0	979735000.0	1006601000.0	862428000.0	889969000.0	920624000.0	910674000.0	925317000.0	877461000.0	582822000.0	455723000.0	312691000.0	284672000.0	289675000.0	302183000.0	489371000.0	442689000.0
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
Percentage of Assets	57.7	0.0	44.4	42.7	43.9	0.0	43.8	43.9	44.5	0.0	45.8	49.7	49.3	47.6	46.5	44.8	40.4	44.3	39.1	32.0	25.9	26.5	27.3	55.5	47.3

us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents

us-gaap:CommonClassA, us-gaap:CommonStockIncludingAdditionalPaidInCapital

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	1209865000.0	1209491000.0	1209023000.0	1208461000.0	1208219000.0	1208065000.0	1207397000.0	1207177000.0	1206953000.0	1206805000.0	1206466000.0	1055037000.0	1054821000.0	1040669000.0	1032876000.0	1032687000.0	1032239000.0	836536000.0	785515000.0	673841000.0	673092000.0	672435000.0	588316000.0	481211000.0
Percentage of StockholdersEquity	101.2	110.2	122.1	130.5	127.7	125.8	127.5	129.1	126.7	123.2	119.9	122.3	118.5	113.0	113.4	111.6	117.6	143.5	172.4	215.5	236.4	222.5	120.2	108.7
Percentage of Assets	58.4	0.0	54.2	55.7	56.1	0.0	55.9	56.7	56.4	0.0	54.9	60.8	58.5	53.9	52.8	50.0	47.6	63.7	67.4	68.9	61.3	60.8	66.7	51.4
Percentage of Assets us-gaap:CommonClassA us-gaap:CommonStockIncludingAdditionalPaidInCapital	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	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:CommonClassB, us-gaap:CommonStockIncludingAdditionalPaidInCapital

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	62635000.0	62635000.0	62635000.0	62635000.0	17135000.0	17135000.0	125000.0	125000.0	125000.0	125000.0	125000.0
Percentage of StockholdersEquity	7.4	8.1	8.9	9.6	9.4	9.2	9.3	9.5	9.3	9.0	8.8	10.3	9.9	6.8	6.9	6.8	7.1	2.9	3.8	0.0	0.0	0.0	0.0	0.0
Percentage of Assets	4.3	0.0	4.0	4.1	4.1	0.0	4.1	4.2	4.1	0.0	4.0	5.1	4.9	3.2	3.2	3.0	2.9	1.3	1.5	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:CommonClassB us-gaap:CommonStockIncludingAdditionalPaidInCapital	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	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:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31	2011-12-31
Value	-102598000.0	-200796000.0	-307635000.0	-370706000.0	-350856000.0	-336549000.0	-348996000.0	-360498000.0	-343015000.0	-315602000.0	-288397000.0	-281141000.0	-253384000.0	-182680000.0	-184837000.0	-170005000.0	-217413000.0	-270849000.0	-346927000.0	-361275000.0	-388545000.0	-370377000.0	-99070000.0
Percentage of StockholdersEquity	-8.6	-18.3	-31.1	-40.0	-37.1	-35.1	-36.9	-38.5	-36.0	-32.2	-28.7	-32.6	-28.5	-19.8	-20.3	-18.4	-24.8	-46.5	-76.1	-115.5	-136.5	-122.6	-20.2
Percentage of Assets	-5.0	0.0	-13.8	-17.1	-16.3	0.0	-16.1	-16.9	-16.0	0.0	-13.1	-16.2	-14.1	-9.5	-9.4	-8.2	-10.0	-20.6	-29.8	-37.0	-35.4	-33.5	-11.2
Percentage of Assets us-gaap:RetainedEarnings	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Stockholders Equity

us-gaap:AssetsCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	348917000.0	421225000.0	261544000.0	228478000.0	225591000.0	177799000.0	168329000.0	176685000.0	149187000.0	178992000.0	215484000.0	186814000.0	251181000.0	279814000.0	191760000.0	253614000.0	83241000.0	215071000.0	204721000.0	202965000.0	36747000.0	38037000.0
Percentage of AssetsCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	16.8	18.9	12.1	10.6	10.4	8.4	7.9	8.0	8.6	9.9	11.2	9.5	12.2	12.9	14.6	21.8	8.5	19.6	18.8	18.4	4.2	4.1

Assets Current

us-gaap:CashAndCashEquivalentsAtCarryingValue

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2012-06-30	2011-12-31	2010-12-31	2009-12-31	2008-12-31
Value	167907000.0	88824000.0	76705000.0	35429000.0	54917000.0	54361000.0	48457000.0	71439000.0	60606000.0	87255000.0	68108000.0	59237000.0	58018000.0	96417000.0	80579000.0	83082000.0	162797000.0	21764000.0	25646000.0	37708000.0	26341000.0	18554000.0	15859000.0	12450000.0	10432000.0	26698000.0
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
Percentage of Assets	8.1	4.0	3.5	1.6	2.5	2.6	2.3	3.3	3.5	4.8	3.5	3.0	2.8	4.4	0.0	6.3	14.0	2.2	2.3	3.5	2.4	0.0	1.8	1.3	0.0	0.0

us-gaap:LongLivedAssetsHeldForSaleByAssetType

us-gaap:CashAndCashEquivalents

Period End	2020-06-30	2019-12-31	2019-06-30	2018-12-31
Value	0.0	1121000.0	0.0	0.0
Percentage of CashAndCashEquivalentsAtCarryingValue	0.0	1.3	0.0	0.0
Percentage of Assets	0.0	0.1	0.0	0.0
Percentage of Assets us-gaap:CashAndCashEquivalents	0.0	0.0	0.0	0.0

Cash And Cash Equivalents At Carrying Value

us-gaap:AccountsReceivableNetCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	88663000.0	95648000.0	52245000.0	51451000.0	17365000.0	17048000.0	15912000.0	19288000.0	22484000.0	18187000.0	30247000.0	25245000.0	43611000.0	28313000.0	11344000.0	4178000.0	2545000.0	4247000.0	7633000.0	4523000.0	157000.0	175000.0
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	4.3	4.3	2.4	2.4	0.8	0.8	0.7	0.9	1.3	1.0	1.6	1.3	2.1	1.3	0.9	0.4	0.3	0.4	0.7	0.4	0.0	0.0

Accounts Receivable Net Current

us-gaap:InventoryNet

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	30885000.0	49790000.0	50473000.0	63441000.0	23179000.0
Percentage of InventoryNet	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	1.5	2.2	2.3	2.9	1.1

Inventory Net

us-gaap:PropertyPlantAndEquipmentNet

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	1683734000.0	1769726000.0	1859733000.0	1875855000.0	1401551000.0	1556959000.0	1695722000.0	1737792000.0	1283989000.0	1554055000.0	1605372000.0	1664859000.0	1706288000.0	1767925000.0	1035311000.0	828291000.0	841013000.0	859308000.0	867035000.0	885992000.0	1310496000.0	1435478000.0
Percentage of PropertyPlantAndEquipmentNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	81.3	79.4	85.7	87.1	64.9	73.1	79.2	79.1	74.0	86.2	83.1	85.0	82.7	81.5	78.8	71.1	86.0	78.3	79.4	80.1	148.6	153.3

Property Plant And Equipment Net

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2013-12-31	2013-06-30	2012-12-31
Value	29740000.0	28112000.0	26418000.0	26351000.0	25766000.0	24811000.0	25170000.0	25460000.0	42927000.0	43201000.0	81273000.0	78771000.0	77862000.0	86808000.0	79566000.0	73397000.0	8366000.0	7289000.0	3457000.0
Percentage of InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	1.4	1.3	1.2	1.2	1.2	1.2	1.2	1.2	2.5	2.4	4.2	4.0	3.8	4.0	6.1	6.3	0.8	0.7	0.3

Investments In Affiliates Subsidiaries Associates And Joint Ventures

us-gaap:Goodwill

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2011-12-31	2010-12-31
Value	2426000.0	2426000.0	8059000.0	8059000.0	8059000.0	8059000.0	8059000.0	8059000.0	8059000.0	8059000.0	8059000.0	8059000.0	8059000.0	0.0	0.0	13310000.0
Percentage of Goodwill	100.0	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
Percentage of Assets	0.1	0.1	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.4	0.4	0.4	0.4	0.0	0.0	1.4

Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31
Value	2259000.0	2545000.0	9955000.0	10498000.0	11625000.0	12320000.0	13030000.0	14605000.0	15262000.0	16044000.0	17658000.0	18491000.0	19342000.0	29619000.0
Percentage of IntangibleAssetsNetExcludingGoodwill	100.0	100.0	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	0.1	0.5	0.5	0.5	0.6	0.6	0.7	0.9	0.9	0.9	0.9	0.9	1.4

Intangible Assets Net Excluding Goodwill

us-gaap:OtherAssetsNoncurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	1453000.0	1923000.0	910000.0	1010000.0	74000.0	82000.0	92000.0	127000.0	139000.0	155000.0	41000.0	73000.0	82000.0	146000.0	1992000.0	5400000.0	4564000.0	4954000.0	2958000.0	6869000.0	1938000.0	1889000.0
Percentage of OtherAssetsNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.2	0.5	0.5	0.5	0.3	0.6	0.2	0.2

Other Assets Noncurrent

us-gaap:LiabilitiesCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	185818000.0	279705000.0	295414000.0	269501000.0	197761000.0	179231000.0	241927000.0	236714000.0	223623000.0	224096000.0	236922000.0	222093000.0	228798000.0	289652000.0	187787000.0	79718000.0	86507000.0	70194000.0	72748000.0	61830000.0	22076000.0	24528000.0
Percentage of LiabilitiesCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	9.0	12.5	13.6	12.5	9.2	8.4	11.3	10.8	12.9	12.4	12.3	11.3	11.1	13.4	14.3	6.8	8.8	6.4	6.7	5.6	2.5	2.6

Liabilities Current

us-gaap:LongTermDebtCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	27549000.0	43573000.0	101295000.0	101264000.0	106236000.0	103843000.0	155089000.0	166745000.0	159087000.0	150254000.0	171019000.0	155690000.0	151761000.0	174047000.0	144453000.0	41959000.0	51959000.0	25246000.0	25246000.0	25246000.0	1800000.0	1800000.0
Percentage of LongTermDebtCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	1.3	2.0	4.7	4.7	4.9	4.9	7.2	7.6	9.2	8.3	8.8	8.0	7.4	8.0	11.0	3.6	5.3	2.3	2.3	2.3	0.2	0.2

Long Term Debt Current

us-gaap:AccountsPayableCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	59652000.0	70978000.0	54824000.0	47532000.0	11146000.0	5352000.0	5822000.0	7860000.0	10353000.0	9253000.0	12265000.0	9858000.0	10784000.0	16717000.0	5747000.0	1899000.0	3388000.0	2251000.0	2098000.0	3346000.0	1935000.0	2124000.0
Percentage of AccountsPayableCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	2.9	3.2	2.5	2.2	0.5	0.3	0.3	0.4	0.6	0.5	0.6	0.5	0.5	0.8	0.4	0.2	0.3	0.2	0.2	0.3	0.2	0.2

Accounts Payable Current

us-gaap:AccruedLiabilitiesCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	40360000.0	59735000.0	46519000.0	56448000.0	40856000.0	35717000.0	34063000.0	34608000.0	29756000.0	26157000.0	27224000.0	26259000.0	47121000.0	62029000.0	18218000.0	17565000.0	14971000.0	21069000.0	14543000.0	17882000.0	7423000.0	7949000.0
Percentage of AccruedLiabilitiesCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	1.9	2.7	2.1	2.6	1.9	1.7	1.6	1.6	1.7	1.5	1.4	1.3	2.3	2.9	1.4	1.5	1.5	1.9	1.3	1.6	0.8	0.8

Accrued Liabilities Current

us-gaap:OperatingLeaseLiabilityCurrent

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	10986000.0	16290000.0	16405000.0	12224000.0	0.0
Percentage of OperatingLeaseLiabilityCurrent	100.0	100.0	100.0	100.0	0.0
Percentage of Assets	0.5	0.7	0.8	0.6	0.0

Operating Lease Liability Current

us-gaap:OtherLiabilitiesCurrent

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	8485000.0	8567000.0	255000.0	316000.0	0.0	528000.0	130000.0	115000.0	277000.0
Percentage of OtherLiabilitiesCurrent	100.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.4	0.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Other Liabilities Current

us-gaap:ProductOrService

us-gaap:ContractWithCustomerLiabilityCurrent

tnk:Timecharter

Period End	2020-06-30	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	7700000.0	7500000.0	0.0	100000.0	0.0	500000.0
Percentage of ContractWithCustomerLiabilityCurrent	100.0	100.0	0.0	100.0	0.0	100.0
Percentage of Assets	0.4	0.3	0.0	0.0	0.0	0.0
Percentage of Assets tnk:Timecharter	0.0	0.0	0.0	0.0	0.0	0.0

Contract With Customer Liability Current

us-gaap:LongTermDebt

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31
Value	312938000.0	559679000.0	608960000.0	593226000.0	735406000.0	807078000.0	933817000.0	952302000.0	645905000.0	821786000.0	933016000.0	966651000.0	1044270000.0	1164605000.0	674672000.0	656063000.0	609398000.0	744634000.0	730214000.0	735701000.0	908730000.0
Percentage of LongTermDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	15.1	25.1	28.1	27.5	34.0	37.9	43.6	43.3	37.2	45.6	48.3	49.4	50.6	53.7	51.3	56.3	62.3	67.8	66.9	66.5	103.0

us-gaap:DebtInstrument, us-gaap:SubsequentEventType

tnk:TermLoanDue2023, us-gaap:SubsequentEvent

Period End	2020-08-01
Value	67400000.0
Percentage of LongTermDebt	0.0
Percentage of Assets	0.0
Percentage of Assets tnk:TermLoanDue2023 us-gaap:SubsequentEvent	0.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	312938000.0	559679000.0	608960000.0	593226000.0	735406000.0
Percentage of LongTermDebt	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	15.1	25.1	28.1	27.5	34.0
Percentage of Assets us-gaap:FairValueInputsLevel2 us-gaap:CarryingReportedAmountFairValueDisclosure us-gaap:FairValueMeasurementsRecurring	0.0	0.0	0.0	0.0	0.0

us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31
Value	314792000.0	558657000.0
Percentage of LongTermDebt	100.6	99.8
Percentage of Assets	15.2	25.1
Percentage of Assets us-gaap:FairValueInputsLevel2 us-gaap:EstimateOfFairValueFairValueDisclosure us-gaap:FairValueMeasurementsRecurring	0.0	0.0

Long Term Debt

us-gaap:LongTermDebtNoncurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	285389000.0	516106000.0	507665000.0	491962000.0	629170000.0	703235000.0	778728000.0	785557000.0	486818000.0	671532000.0	761997000.0	810961000.0	892509000.0	990558000.0	530219000.0	614104000.0	557439000.0	719388000.0	704968000.0	710455000.0	347100000.0	452228000.0
Percentage of LongTermDebtNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	13.8	23.1	23.4	22.8	29.1	33.0	36.4	35.8	28.0	37.2	39.4	41.4	43.2	45.7	40.3	52.7	57.0	65.5	64.6	64.3	39.4	48.3

Long Term Debt Noncurrent

us-gaap:OtherLiabilitiesNoncurrent

Period End	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	2016-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31	2009-12-31
Value	27516000.0	51044000.0	37474000.0	37166000.0	32829000.0	30646000.0	29620000.0	26795000.0	19226000.0	17829000.0	13683000.0	5444000.0	5351000.0	4902000.0	4757000.0	3228000.0	2733000.0	4102000.0
Percentage of OtherLiabilitiesNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	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	1.3	2.3	1.7	1.7	1.5	1.4	1.4	1.2	1.1	1.0	0.7	0.6	0.5	0.4	0.4	0.4	0.3	0.0

Other Liabilities Noncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	417000.0	3270000.0	7190000.0	6865000.0	0.0
Percentage of OperatingLeaseLiabilityNoncurrent	100.0	100.0	100.0	100.0	0.0
Percentage of Assets	0.0	0.1	0.3	0.3	0.0

Operating Lease Liability Noncurrent

us-gaap:StockholdersEquity

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	1195799000.0	1097227000.0	989920000.0	926287000.0	945895000.0	960048000.0	946933000.0	935211000.0	952470000.0	979735000.0	1006601000.0	862428000.0	889969000.0	920624000.0	910674000.0	925317000.0	877461000.0	582822000.0	455723000.0	312691000.0	284672000.0	289675000.0	302183000.0	489371000.0	442689000.0
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
Percentage of Assets	57.7	0.0	44.4	42.7	43.9	0.0	43.8	43.9	44.5	0.0	45.8	49.7	49.3	47.6	46.5	44.8	40.4	44.3	39.1	32.0	25.9	26.5	27.3	55.5	47.3

us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents

us-gaap:CommonClassA, us-gaap:CommonStockIncludingAdditionalPaidInCapital

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	1209865000.0	1209491000.0	1209023000.0	1208461000.0	1208219000.0	1208065000.0	1207397000.0	1207177000.0	1206953000.0	1206805000.0	1206466000.0	1055037000.0	1054821000.0	1040669000.0	1032876000.0	1032687000.0	1032239000.0	836536000.0	785515000.0	673841000.0	673092000.0	672435000.0	588316000.0	481211000.0
Percentage of StockholdersEquity	101.2	110.2	122.1	130.5	127.7	125.8	127.5	129.1	126.7	123.2	119.9	122.3	118.5	113.0	113.4	111.6	117.6	143.5	172.4	215.5	236.4	222.5	120.2	108.7
Percentage of Assets	58.4	0.0	54.2	55.7	56.1	0.0	55.9	56.7	56.4	0.0	54.9	60.8	58.5	53.9	52.8	50.0	47.6	63.7	67.4	68.9	61.3	60.8	66.7	51.4
Percentage of Assets us-gaap:CommonClassA us-gaap:CommonStockIncludingAdditionalPaidInCapital	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	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:CommonClassB, us-gaap:CommonStockIncludingAdditionalPaidInCapital

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	88532000.0	62635000.0	62635000.0	62635000.0	62635000.0	17135000.0	17135000.0	125000.0	125000.0	125000.0	125000.0	125000.0
Percentage of StockholdersEquity	7.4	8.1	8.9	9.6	9.4	9.2	9.3	9.5	9.3	9.0	8.8	10.3	9.9	6.8	6.9	6.8	7.1	2.9	3.8	0.0	0.0	0.0	0.0	0.0
Percentage of Assets	4.3	0.0	4.0	4.1	4.1	0.0	4.1	4.2	4.1	0.0	4.0	5.1	4.9	3.2	3.2	3.0	2.9	1.3	1.5	0.0	0.0	0.0	0.0	0.0
Percentage of Assets us-gaap:CommonClassB us-gaap:CommonStockIncludingAdditionalPaidInCapital	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	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:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31	2011-12-31
Value	-102598000.0	-200796000.0	-307635000.0	-370706000.0	-350856000.0	-336549000.0	-348996000.0	-360498000.0	-343015000.0	-315602000.0	-288397000.0	-281141000.0	-253384000.0	-182680000.0	-184837000.0	-170005000.0	-217413000.0	-270849000.0	-346927000.0	-361275000.0	-388545000.0	-370377000.0	-99070000.0
Percentage of StockholdersEquity	-8.6	-18.3	-31.1	-40.0	-37.1	-35.1	-36.9	-38.5	-36.0	-32.2	-28.7	-32.6	-28.5	-19.8	-20.3	-18.4	-24.8	-46.5	-76.1	-115.5	-136.5	-122.6	-20.2
Percentage of Assets	-5.0	0.0	-13.8	-17.1	-16.3	0.0	-16.1	-16.9	-16.0	0.0	-13.1	-16.2	-14.1	-9.5	-9.4	-8.2	-10.0	-20.6	-29.8	-37.0	-35.4	-33.5	-11.2
Percentage of Assets us-gaap:RetainedEarnings	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Stockholders Equity

us-gaap:CommonStocksIncludingAdditionalPaidInCapital

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31
Value	1298397000.0	1297555000.0	1296993000.0	1296751000.0	1295929000.0	1295709000.0	1295485000.0	1294998000.0	1143569000.0	1143353000.0	1103304000.0	1095511000.0	1095322000.0	1094874000.0	853671000.0	802650000.0	673966000.0	673217000.0	672744000.0	672560000.0
Percentage of CommonStocksIncludingAdditionalPaidInCapital	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	62.7	58.2	59.8	60.2	60.0	60.9	60.5	58.9	65.9	63.4	57.1	56.0	53.1	50.5	65.0	68.9	68.9	61.3	61.6	60.8

Common Stocks Including Additional Paid In Capital

us-gaap:RetainedEarningsAccumulatedDeficit

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	-102598000.0	-307635000.0	-370706000.0	-350856000.0	-348996000.0	-360498000.0	-343015000.0	-288397000.0	-281141000.0	-253384000.0	-182680000.0	-184837000.0	-170005000.0	-217413000.0	-270849000.0	-346927000.0	-361275000.0	-388545000.0	-383069000.0	-370377000.0	-99070000.0	-38647000.0
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
Percentage of Assets	-5.0	-13.8	-17.1	-16.3	-16.1	-16.9	-16.0	-13.1	-16.2	-14.1	-9.5	-9.4	-8.2	-10.0	-20.6	-29.8	-37.0	-35.4	-35.1	-33.5	-11.2	-4.1

Retained Earnings Accumulated Deficit

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

Period End	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	2016-12-31	2016-09-30
Value	374000.0	468000.0	242000.0	154000.0	668000.0	235000.0	224000.0	148000.0	613000.0	167000.0	216000.0	235000.0	189000.0
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
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

us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents

us-gaap:CommonClassA, us-gaap:CommonStockIncludingAdditionalPaidInCapital

Period End	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	2016-12-31	2016-09-30
Value	374000.0	468000.0	242000.0	154000.0	668000.0	235000.0	224000.0	148000.0	613000.0	167000.0	216000.0	235000.0	189000.0
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
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
Percentage of Assets us-gaap:CommonClassA us-gaap:CommonStockIncludingAdditionalPaidInCapital	0.0	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:ProfitLoss

Period End	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	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	98198000.0	106839000.0	63072000.0	-19850000.0	-14307000.0	12447000.0	11502000.0	-17484000.0	-27413000.0	-19153000.0	-1879000.0	-22380000.0	-37477000.0	6846000.0	-5457000.0	22486000.0	53559000.0	40950000.0	44242000.0	4589000.0	-5724000.0	-4323000.0
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
Percentage of Revenues	39.8	0.0	19.3	-10.9	-7.1	0.0	4.8	-9.9	-16.0	0.0	-1.9	-24.5	-34.4	5.8	-5.2	16.1	31.7	32.4	41.1	10.3	-13.2	-8.5

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	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	2016-12-31	2016-09-30
Value	98198000.0	106839000.0	-19850000.0	-14307000.0	12447000.0	11502000.0	-17484000.0	-27413000.0	-19153000.0	-1879000.0	-22380000.0	6846000.0	-5457000.0
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
Percentage of Revenues	39.8	0.0	-10.9	-7.1	0.0	4.8	-9.9	-16.0	0.0	-1.9	-24.5	5.8	-5.2
Percentage of Revenues us-gaap:RetainedEarnings	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Profit Loss

us-gaap:UnrecognizedTaxBenefits

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2019-01-01	2018-12-31	2018-09-30	2018-06-30	2018-01-01	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2014-12-31	2013-12-31
Value	35749000.0	49579000.0	36240000.0	35792000.0	32059000.0	32059000.0	29912000.0	28911000.0	26054000.0	26054000.0	18471000.0	17061000.0	12882000.0	11208000.0	11844000.0	7597000.0	4852000.0	5351000.0
Percentage of UnrecognizedTaxBenefits	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Unrecognized Tax Benefits

us-gaap:OperatingLeaseRightOfUseAsset

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	10758000.0	19600000.0	23595000.0	19089000.0	0.0
Percentage of OperatingLeaseRightOfUseAsset	100.0	100.0	100.0	100.0	0.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsNonrecurring

Period End	2020-06-30
Value	10758000.0
Percentage of OperatingLeaseRightOfUseAsset	100.0

us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsNonrecurring

Period End	2020-06-30
Value	10758000.0
Percentage of OperatingLeaseRightOfUseAsset	100.0

Operating Lease Right Of Use Asset

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

Period End	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	2016-12-31	2015-12-31
Value	176110000.0	96790000.0	82483000.0	40782000.0	60507000.0	58827000.0	52987000.0	75710000.0	64923000.0	88635000.0	94907000.0	157390000.0
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

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel1, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	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	2016-12-31	2015-12-31
Value	176110000.0	95332000.0	82483000.0	40782000.0	60507000.0	58827000.0	72007000.0	75710000.0	64923000.0	88635000.0	94907000.0	157390000.0
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	100.0	98.5	100.0	100.0	100.0	100.0	135.9	100.0	100.0	100.0	100.0	100.0

us-gaap:FairValueInputsLevel1, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	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	2016-12-31	2015-12-31
Value	176110000.0	95332000.0	82483000.0	40782000.0	60507000.0	58827000.0	72007000.0	75710000.0	64923000.0	88635000.0	94907000.0	157390000.0
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	100.0	98.5	100.0	100.0	100.0	100.0	135.9	100.0	100.0	100.0	100.0	100.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

tnk:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRealizedGainLossNet

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30
Value	-114000.0	1492000.0	1048000.0	800000.0	1015000.0	592000.0	656000.0	-177000.0	80000.0	139000.0	280000.0	-181000.0	-1150000.0	-2398000.0	-2476000.0	-2452000.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRealizedGainLossNet	100.0	100.0	100.0	100.0	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:DerivativeInstrumentRisk

tnk:FreightForwardAgreements

Period End	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	2016-12-31	2016-09-30	2016-06-30
Value	-200000.0	1096000.0	435000.0	-29000.0	274000.0	-119000.0	-18000.0	-77000.0	234000.0	80000.0	0.0	0.0	0.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRealizedGainLossNet	175.4	73.5	41.5	-3.6	27.0	-20.1	-2.7	43.5	292.5	57.6	0.0	-0.0	-0.0

us-gaap:InterestRateSwap

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2013-06-30	2012-06-30
Value	86000.0	396000.0	613000.0	829000.0	741000.0	711000.0	674000.0	-100000.0	-154000.0	-301000.0	-652000.0	-1277000.0	-1276000.0	-2398000.0	-2476000.0	-2452000.0	2500000.0	2400000.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRealizedGainLossNet	-75.4	26.5	58.5	103.6	73.0	120.1	102.7	56.5	-192.5	-216.5	-232.9	705.5	111.0	100.0	100.0	100.0	0.0	0.0

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities, us-gaap:StatementClassOfStock

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

us-gaap:EmployeeStockOption, us-gaap:CommonClassA

Period End	2020-06-30	2019-06-30	2018-09-30	2018-06-30	2017-09-30	2017-06-30	2016-09-30	2016-06-30
Value	200000.0	15000.0	2900000.0	2900000.0	1700000.0	1700000.0	800000.0	800000.0
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DepreciationAndAmortization

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	29546000.0	31943000.0	31536000.0	30658000.0	29916000.0	29595000.0	29573000.0	26829000.0	24328000.0	24415000.0	25573000.0	25888000.0	25621000.0	25414000.0	17878000.0	15227000.0	12425000.0	11921000.0	18047000.0
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

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:ShipToShipTransfer

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30
Value	121000.0	897000.0	902000.0	733000.0	1025000.0	1063000.0	1119000.0	1253000.0	1257000.0	1258000.0	1474000.0	1237000.0	1301000.0	998000.0	644000.0
Percentage of DepreciationAndAmortization	0.4	2.8	2.9	2.4	3.4	3.6	3.8	4.7	5.2	5.2	5.8	4.8	5.1	3.9	3.6

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	29425000.0	29925000.0
Percentage of DepreciationAndAmortization	99.6	97.6

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30
Value	-589000.0	205000.0	1453000.0	-1778000.0	-1693000.0	596000.0	1116000.0	2028000.0	390000.0	-1560000.0	6938000.0	3629000.0	-3750000.0	498000.0	-1031000.0	523000.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	100.0	100.0	100.0	100.0	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:DerivativeInstrumentRisk

tnk:FreightForwardAgreements

Period End	2020-06-30	2019-09-30	2019-06-30	2018-09-30	2018-06-30	2017-09-30	2017-06-30	2016-09-30	2016-06-30
Value	-192000.0	1381000.0	92000.0	-128000.0	16000.0	143000.0	50000.0	0.0	0.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	32.6	95.0	-5.2	-21.5	1.4	36.7	-3.2	0.0	-0.0

us-gaap:InterestRateSwap

Period End	2020-06-30	2019-09-30	2019-06-30	2018-09-30	2018-06-30	2017-09-30	2017-06-30	2016-09-30	2016-06-30	2015-09-30	2015-06-30
Value	-397000.0	72000.0	-1870000.0	724000.0	1100000.0	247000.0	-1402000.0	2523000.0	-3084000.0	-926000.0	-386000.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	67.4	5.0	105.2	121.5	98.6	63.3	89.9	69.5	82.2	89.8	-73.8

us-gaap:IncomeStatementLocation

us-gaap:EmployeeBenefitsAndShareBasedCompensation

us-gaap:GeneralAndAdministrativeExpense

Period End	2020-06-30	2019-06-30
Value	600000.0	200000.0
Percentage of EmployeeBenefitsAndShareBasedCompensation	100.0	100.0

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30
Value	-87000.0	-614000.0	918000.0	595000.0	-2892000.0	1251000.0	4794000.0	-72000.0	81000.0	-3000.0	1723000.0	-35000.0	-76000.0	406000.0	-42000.0	-65000.0
Percentage of ForeignCurrencyTransactionGainLossBeforeTax	100.0	100.0	100.0	100.0	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:PropertyPlantAndEquipmentByType

us-gaap:GainLossOnDispositionOfAssets

tnk:SuezmaxTankerHeldForSale

Period End	2020-06-30	2020-03-31
Value	500000.0	-500000.0
Percentage of GainLossOnDispositionOfAssets	100.0	100.0

us-gaap:SubsequentEventType

us-gaap:GainLossOnSaleOfPropertyPlantEquipment

us-gaap:SubsequentEvent

Period End	2020-03-31
Value	2700000.0
Percentage of GainLossOnSaleOfPropertyPlantEquipment	100.0

us-gaap:GainLossOnSalesOfAssetsAndAssetImpairmentCharges

Period End	2020-06-30	2019-06-30
Value	2896000.0	0.0
Percentage of GainLossOnSalesOfAssetsAndAssetImpairmentCharges	100.0	0.0

us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:ShipToShipTransfer

Period End	2020-06-30
Value	3081000.0
Percentage of GainLossOnSalesOfAssetsAndAssetImpairmentCharges	106.4

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30
Value	-185000.0
Percentage of GainLossOnSalesOfAssetsAndAssetImpairmentCharges	-6.4

us-gaap:IncomeLossFromEquityMethodInvestments

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30
Value	3188000.0	1648000.0	68000.0	-169000.0	955000.0	-359000.0	-70000.0	1774000.0	-274000.0	-28027000.0	3501000.0	1045000.0	4740000.0	5480000.0	2762000.0	3587000.0	15000.0	-167000.0
Percentage of IncomeLossFromEquityMethodInvestments	100.0	100.0	100.0	100.0	100.0	100.0	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:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	3188000.0	-169000.0
Percentage of IncomeLossFromEquityMethodInvestments	100.0	100.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30
Value	250752.0	113536.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	-24052.0	0.0	237978.0	10685.0	543988.0	574443.0	290449.0
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	100.0	100.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InvestmentIncomeInterest

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30
Value	567000.0	147000.0	138000.0	221000.0	311000.0	250000.0	160000.0	163000.0	305000.0	360000.0	47000.0	18000.0	26000.0	40000.0	28000.0	8000.0	60000.0	20000.0
Percentage of InvestmentIncomeInterest	100.0	100.0	100.0	100.0	100.0	100.0	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:LeaseAndRentalExpense

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30	2012-06-30
Value	9296000.0	12312000.0	10637000.0	10792000.0	4841000.0	4317000.0	5697000.0	3202000.0	5835000.0	7997000.0	11683000.0	11335000.0	15913000.0	21720000.0	21382000.0	16793000.0	1112000.0	1951000.0	644000.0
Percentage of LeaseAndRentalExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, tnk:ShipToShipTransfer

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30
Value	0.0	1584000.0	1306000.0	0.0	1630000.0	1382000.0	1584000.0	1234000.0	1206000.0	1062000.0	985000.0	551000.0	457000.0	0.0	38000.0
Percentage of LeaseAndRentalExpense	0.0	12.9	12.3	0.0	33.7	32.0	27.8	38.5	20.7	13.3	8.4	4.9	2.9	0.0	0.2

us-gaap:OperatingSegments, tnk:Tankers

Period End	2020-06-30	2019-06-30
Value	9296000.0	10792000.0
Percentage of LeaseAndRentalExpense	100.0	100.0

us-gaap:OtherNonoperatingIncome

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30
Value	1027000.0	127000.0	15000.0	19000.0	0.0	0.0	19000.0	23000.0	15000.0	186000.0	-34000.0	0.0	160000.0	49000.0	0.0	0.0
Percentage of OtherNonoperatingIncome	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	0.0	0.0

us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:StatementBusinessSegments

us-gaap:ProceedsFromDivestitureOfBusinesses

tnk:ShipToShipTransferBusiness, tnk:ShipToShipTransferBusiness

Period End	2020-06-30	2020-04-30
Value	27100000.0	14300000.0
Percentage of ProceedsFromDivestitureOfBusinesses	100.0	100.0

us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:StatementBusinessSegments, us-gaap:SubsequentEventType

tnk:ShipToShipTransferBusiness, tnk:ShipToShipTransferBusiness, us-gaap:SubsequentEvent

Period End	2020-07-31
Value	12700000.0
Percentage of ProceedsFromDivestitureOfBusinesses	0.0

us-gaap:RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30	2014-06-30	2013-06-30
Value	7143000.0	8243000.0	7437000.0	7950000.0	7714000.0	7875000.0	8633000.0	7507000.0	6761000.0	4253000.0	2661000.0	2471000.0	2775000.0	3043000.0	1594000.0	1777000.0	2466000.0	2717000.0
Percentage of RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty	100.0	100.0	100.0	100.0	100.0	100.0	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:RelatedPartyTransaction

tnk:SecondmentFees

Period End	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	2016-12-31	2016-09-30
Value	144000.0	65000.0	21000.0	40000.0	131000.0	189000.0	142000.0	194000.0	148000.0	0.0	0.0	0.0
Percentage of RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty	2.0	0.8	0.3	0.5	1.7	2.4	1.6	2.6	2.2	0.0	0.0	0.0

us-gaap:RelatedPartyTransaction

us-gaap:RevenueFromRelatedParties

tnk:LNGterminalservices

Period End	2020-06-30	2019-09-30	2019-06-30	2018-09-30	2018-06-30	2017-09-30	2017-06-30	2016-09-30	2016-06-30
Value	0.0	-150000.0	1000000.0	72000.0	31000.0	84000.0	84000.0	0.0	0.0
Percentage of RevenueFromRelatedParties	0.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0

tnk:Technicalmanagementfeerevenue

Period End	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	2016-12-31	2016-09-30
Value	169000.0	169000.0	169000.0	169000.0	3992000.0	3490000.0	3171000.0	2618000.0	3828000.0	1220000.0	0.0	0.0
Percentage of RevenueFromRelatedParties	0.0	0.0	-112.7	16.9	0.0	4847.2	10229.0	0.0	4557.1	1452.4	0.0	0.0

us-gaap:OtherIncome

Period End	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	2016-12-31	2016-09-30	2016-06-30
Value	0.0	3000.0	100000.0	67000.0	261000.0	343000.0	254000.0	659000.0	1003000.0	277000.0	0.0	0.0	0.0
Percentage of RevenueFromRelatedParties	0.0	0.0	-66.7	6.7	0.0	476.4	819.4	0.0	1194.0	329.8	0.0	0.0	0.0

us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesEmployeeBenefitPlan

us-gaap:CommonStockIncludingAdditionalPaidInCapital

Period End	2020-06-30	2020-03-31	2019-06-30	2019-03-31	2018-06-30	2018-03-31
Value	26000.0	57000.0	0.0	432000.0	0.0	357000.0
Percentage of StockIssuedDuringPeriodSharesEmployeeBenefitPlan	100.0	100.0	0.0	100.0	0.0	100.0

us-gaap:UnrealizedGainLossOnDerivatives

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30
Value	-475000.0	-1287000.0	405000.0	-2578000.0	-2708000.0	4000.0	460000.0	2205000.0	310000.0	-1699000.0	6658000.0	3810000.0	-2600000.0	2896000.0	1445000.0	2975000.0
Percentage of UnrealizedGainLossOnDerivatives	100.0	100.0	100.0	100.0	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:DerivativeInstrumentRisk

tnk:FreightForwardAgreements

Period End	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	2016-12-31	2016-09-30	2016-06-30
Value	8000.0	-1079000.0	946000.0	121000.0	-82000.0	-9000.0	34000.0	108000.0	-91000.0	-30000.0	0.0	0.0	0.0
Percentage of UnrealizedGainLossOnDerivatives	-1.7	83.8	233.6	-4.7	3.0	-225.0	7.4	4.9	-29.4	1.8	0.0	0.0	-0.0

us-gaap:InterestRateSwap

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-09-30	2015-06-30
Value	-483000.0	-208000.0	-541000.0	-2699000.0	-2626000.0	13000.0	426000.0	2097000.0	401000.0	-1101000.0	7767000.0	3800000.0	-1808000.0	3153000.0	1550000.0	2066000.0
Percentage of UnrealizedGainLossOnDerivatives	101.7	16.2	-133.6	104.7	97.0	325.0	92.6	95.1	129.4	64.8	116.7	99.7	69.5	108.9	107.3	69.4

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis

tnk:AccruedLiabilitiesReceivablesCurrent

tnk:FreightForwardAgreements, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-09-30	2018-06-30
Value	0.0	0.0	4000.0	8000.0
Percentage of AccruedLiabilitiesReceivablesCurrent	0.0	0.0	100.0	100.0

us-gaap:InterestRateSwap, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-09-30	2018-06-30	2017-12-31
Value	0.0	230000.0	-394000.0	-389000.0	39000.0
Percentage of AccruedLiabilitiesReceivablesCurrent	0.0	0.0	-9850.0	-4862.5	0.0

us-gaap:FairValueByMeasurementBasis

us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-09-30	2018-06-30	2017-12-31
Value	0.0	230000.0	-390000.0	-381000.0	39000.0
Percentage of AccruedLiabilitiesReceivablesCurrent	0.0	0.0	-9750.0	-4762.5	0.0

us-gaap:DebtInstrument

tnk:ActualHullCoverageRatio

tnk:A2020DebtFacilityMaturinginDecember2024

Period End	2020-06-30
Value	3.79
Percentage of ActualHullCoverageRatio	100.0

us-gaap:PropertyPlantAndEquipmentByType, us-gaap:SaleLeasebackTransactionDescription

tnk:SuezmaxAframaxandLR2SaleLeaseback, tnk:November2018SaleleasebackTransaction

Period End	2020-06-30	2019-12-31	2019-09-30	2018-12-31
Value	1.63	1.58	1.53	1.22
Percentage of ActualHullCoverageRatio	43.0	0.0	0.0	0.0

us-gaap:SaleLeasebackTransactionDescription

tnk:July2017SaleLeaseback

Period End	2020-06-30	2019-12-31
Value	1.29	1.22
Percentage of ActualHullCoverageRatio	34.0	0.0

tnk:May2019SaleLeaseback

Period End	2020-06-30	2019-12-31
Value	1.02	1.09
Percentage of ActualHullCoverageRatio	26.9	0.0

tnk:September2018SaleLeaseback

Period End	2020-06-30	2019-12-31
Value	1.1	1.15
Percentage of ActualHullCoverageRatio	29.0	0.0

tnk:LeaseObligationType

tnk:DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLine

tnk:FinanceLeaseObligations

Period End	2020-06-30
Value	35000000.0
Percentage of DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLine	100.0

us-gaap:DebtInstrument

tnk:A2020DebtFacilityMaturinginDecember2024

Period End	2020-06-30
Value	35000000.0
Percentage of DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLine	100.0

tnk:TermLoanDue2023

Period End	2020-06-30
Value	35000000.0
Percentage of DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLine	100.0

tnk:LeaseObligationType

tnk:DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLineAsPercentageOfDebt

tnk:FinanceLeaseObligations

Period End	2020-06-30
Value	0.05
Percentage of DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLineAsPercentageOfDebt	100.0

us-gaap:DebtInstrument

tnk:A2020DebtFacilityMaturinginDecember2024

Period End	2020-06-30
Value	0.05
Percentage of DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLineAsPercentageOfDebt	100.0

tnk:TermLoanDue2023

Period End	2020-06-30
Value	0.05
Percentage of DebtCovenantMinimumFreeLiquidityAndUndrawnRevolvingCreditLineAsPercentageOfDebt	100.0

us-gaap:DebtInstrument

tnk:DebtInstrumentCollateralNumberofVessels

tnk:A2020DebtFacilityMaturinginDecember2024

Period End	2020-06-30
Value	31.0
Percentage of DebtInstrumentCollateralNumberofVessels	100.0

us-gaap:DebtInstrument, us-gaap:LongtermDebtType, us-gaap:SubsequentEventType

tnk:TermLoanDue2023, us-gaap:SecuredDebt, us-gaap:SubsequentEvent

Period End	2020-08-01
Value	4.0
Percentage of DebtInstrumentCollateralNumberofVessels	0.0

us-gaap:LongtermDebtType

us-gaap:SecuredDebt

Period End	2020-06-30
Value	4.0
Percentage of DebtInstrumentCollateralNumberofVessels	12.9

us-gaap:AccruedFeesAndOtherRevenueReceivable

Period End	2020-06-30	2019-12-31	2018-12-31
Value	42153000.0	106872000.0	17943000.0
Percentage of AccruedFeesAndOtherRevenueReceivable	100.0	100.0	100.0

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipmentExcludingCapitalLeasedAssets

Period End	2020-06-30	2019-12-31	2018-12-31
Value	563800000.0	537100000.0	494400000.0
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipmentExcludingCapitalLeasedAssets	100.0	100.0	100.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:AdvancesToAffiliate

us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	6430000.0	9930000.0	9930000.0	9930000.0	9930000.0
Percentage of AdvancesToAffiliate	100.0	100.0	100.0	100.0	100.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:AssetsHeldForSaleLongLivedFairValueDisclosure

us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2018-12-31
Value	0.0	37240000.0	0.0
Percentage of AssetsHeldForSaleLongLivedFairValueDisclosure	0.0	100.0	0.0

us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2018-12-31
Value	0.0	37240000.0	0.0
Percentage of AssetsHeldForSaleLongLivedFairValueDisclosure	0.0	100.0	0.0

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent

Period End	2020-06-30	2019-12-31	2018-12-31
Value	0.0	65458000.0	0.0
Percentage of AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent	0.0	100.0	0.0

us-gaap:DebtInstrumentCarryingAmount

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2014-12-31
Value	321681000.0	562861000.0	612877000.0	597925000.0	741992000.0	814709000.0	942974000.0	963247000.0	652233000.0	828856000.0	941661000.0	976155000.0	1054708000.0	1166301000.0	710328000.0
Percentage of DebtInstrumentCarryingAmount	100.0	100.0	100.0	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:DebtInstrument, us-gaap:LongtermDebtType

tnk:A2020DebtFacilityMaturinginDecember2024, us-gaap:RevolvingCreditFacility

Period End	2020-06-30
Value	235000000.0
Percentage of DebtInstrumentCarryingAmount	73.1

us-gaap:LongtermDebtType

us-gaap:RevolvingCreditFacility

Period End	2020-06-30	2019-12-31
Value	235000000.0	341132000.0
Percentage of DebtInstrumentCarryingAmount	73.1	60.6

us-gaap:SecuredDebt

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2014-12-31
Value	86681000.0	221729000.0	248947000.0	273996000.0	323995000.0	348946000.0	373800000.0	423500000.0	330900000.0	417930000.0	475466000.0	509368000.0	543200000.0	635330000.0	147470000.0
Percentage of DebtInstrumentCarryingAmount	26.9	39.4	40.6	45.8	43.7	42.8	39.6	44.0	50.7	50.4	50.5	52.2	51.5	54.5	20.8

us-gaap:ShortTermDebtType

us-gaap:DebtInstrumentInterestRateEffectivePercentage

us-gaap:ShortTermDebt

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	0.037	0.05	0.055	0.059	0.0
Percentage of DebtInstrumentInterestRateEffectivePercentage	100.0	100.0	100.0	100.0	0.0

us-gaap:DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet

Period End	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	2016-12-31
Value	8743000.0	3182000.0	3917000.0	4699000.0	6586000.0	7631000.0	9157000.0	10945000.0	6328000.0	7070000.0	8645000.0
Percentage of DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DerivativeAssetsCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31
Value	0.0	577000.0	1878000.0	1229000.0	2905000.0	3075000.0	2728000.0	1016000.0	233000.0	116000.0	875000.0	1554000.0	1345000.0	0.0
Percentage of DerivativeAssetsCurrent	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

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis

tnk:FreightForwardAgreements, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2018-09-30	2018-06-30
Value	0.0	0.0	0.0	102000.0	34000.0
Percentage of DerivativeAssetsCurrent	0.0	0.0	0.0	3.3	1.2

us-gaap:InterestRateSwap, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31
Value	0.0	577000.0	2905000.0	2973000.0	2694000.0	1016000.0
Percentage of DerivativeAssetsCurrent	0.0	100.0	100.0	96.7	98.8	100.0

us-gaap:FairValueByMeasurementBasis

us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2018-09-30	2018-06-30	2017-12-31	2016-12-31
Value	0.0	577000.0	2905000.0	3075000.0	2728000.0	1016000.0	875000.0
Percentage of DerivativeAssetsCurrent	0.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis

us-gaap:DerivativeAssetsNoncurrent

us-gaap:InterestRateSwap, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2017-12-31	2016-12-31
Value	0.0	82000.0	2973000.0	4226000.0	4251000.0
Percentage of DerivativeAssetsNoncurrent	0.0	100.0	100.0	100.0	100.0

us-gaap:FairValueByMeasurementBasis

us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31
Value	0.0	82000.0	2973000.0	4226000.0	4538000.0	5164000.0
Percentage of DerivativeAssetsNoncurrent	0.0	100.0	100.0	100.0	106.8	0.0

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30
Value	0.0	82000.0	82000.0	240000.0	2973000.0	5531000.0	5797000.0	4226000.0	3022000.0	2920000.0	4538000.0	717000.0	916000.0	5164000.0	5526000.0	4657000.0	4026000.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue	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

us-gaap:DerivativeLiabilitiesCurrent

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31	2018-06-30	2017-12-31	2017-09-30	2017-06-30	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31
Value	414000.0	86000.0	0.0	0.0	57000.0	16000.0	0.0	81000.0	265000.0	1108000.0	1861000.0	3248000.0	6330000.0	7141000.0	7263000.0	7482000.0	7344000.0
Percentage of DerivativeLiabilitiesCurrent	100.0	100.0	0.0	0.0	100.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis

tnk:FreightForwardAgreements, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2018-06-30
Value	-165000.0	86000.0	57000.0	16000.0
Percentage of DerivativeLiabilitiesCurrent	-39.9	100.0	100.0	100.0

us-gaap:InterestRateSwap, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31
Value	-249000.0	0.0	0.0	0.0	1108000.0	6330000.0
Percentage of DerivativeLiabilitiesCurrent	-60.1	0.0	0.0	0.0	100.0	100.0

us-gaap:FairValueByMeasurementBasis

us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2018-12-31	2018-06-30	2017-12-31	2016-12-31	2015-12-31
Value	414000.0	86000.0	57000.0	16000.0	0.0	1108000.0	6330000.0
Percentage of DerivativeLiabilitiesCurrent	100.0	100.0	100.0	100.0	0.0	100.0	100.0

us-gaap:DerivativeLiabilitiesNoncurrent

Period End	2020-06-30	2019-12-31	2019-09-30	2018-12-31	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	789000.0	0.0	49000.0	0.0	0.0	2763000.0	5177000.0	4208000.0	8100000.0	10962000.0	15418000.0	17924000.0	19540000.0	26431000.0	20151000.0	14339000.0
Percentage of DerivativeLiabilitiesNoncurrent	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	100.0	100.0	100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis

us-gaap:InterestRateSwap, us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2015-12-31
Value	789000.0	0.0	4208000.0
Percentage of DerivativeLiabilitiesNoncurrent	100.0	0.0	100.0

us-gaap:FairValueByMeasurementBasis

us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2019-12-31	2015-12-31
Value	789000.0	0.0	4208000.0
Percentage of DerivativeLiabilitiesNoncurrent	100.0	0.0	100.0

us-gaap:DueFromAffiliateCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	2440000.0	697000.0	1634000.0	1240000.0	39663000.0	50551000.0	50034000.0	49103000.0	33314000.0	46306000.0	41420000.0	52501000.0	80075000.0	67159000.0	47493000.0	42502000.0	33197000.0	27991000.0	20981000.0	24787000.0	12610000.0	12357000.0
Percentage of DueFromAffiliateCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:DueToAffiliateCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31	2010-12-31
Value	2091000.0	2139000.0	1241000.0	12320000.0	18570000.0	18391000.0	39422000.0	19717000.0	14293000.0	31993000.0	20912000.0	26470000.0	15409000.0	26630000.0	11830000.0	10395000.0	8707000.0	11323000.0	22375000.0	3592000.0	4999000.0	5841000.0
Percentage of DueToAffiliateCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:RelatedPartyTransaction

tnk:PayabletoManager

Period End	2020-06-30	2019-12-31	2019-09-30	2018-12-31
Value	10100000.0	7900000.0	7800000.0	7600000.0
Percentage of DueToAffiliateCurrent	483.0	369.3	628.5	40.9

us-gaap:FinanceLeaseLiability

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	402519000.0	414788000.0	420934000.0	426936000.0	375289000.0
Percentage of FinanceLeaseLiability	100.0	100.0	100.0	100.0	100.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	402519000.0	414788000.0	420934000.0	426936000.0	375289000.0
Percentage of FinanceLeaseLiability	100.0	100.0	100.0	100.0	100.0

us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	465028000.0	442648000.0	451145000.0	451746000.0	377652000.0
Percentage of FinanceLeaseLiability	115.5	106.7	107.2	105.8	100.6

us-gaap:FinanceLeaseLiabilityCurrent

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	26281000.0	25357000.0	24875000.0	24397000.0	20896000.0
Percentage of FinanceLeaseLiabilityCurrent	100.0	100.0	100.0	100.0	100.0

us-gaap:FinanceLeaseLiabilityNoncurrent

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	376238000.0	389431000.0	396059000.0	402539000.0	354393000.0
Percentage of FinanceLeaseLiabilityNoncurrent	100.0	100.0	100.0	100.0	100.0

tnk:LeaseObligationType

us-gaap:FinanceLeaseLiabilityPaymentsDue

tnk:FinanceLeaseObligations

Period End	2020-06-30	2019-12-31
Value	573900000.0	601700000.0
Percentage of FinanceLeaseLiabilityPaymentsDue	100.0	100.0

tnk:LeaseObligationType

us-gaap:FinanceLeaseLiabilityUndiscountedExcessAmount

tnk:FinanceLeaseObligations

Period End	2020-06-30	2019-12-31
Value	171400000.0	186900000.0
Percentage of FinanceLeaseLiabilityUndiscountedExcessAmount	100.0	100.0

us-gaap:FinanceLeaseRightOfUseAsset

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	511879000.0	527081000.0	525597000.0	529286000.0	482010000.0
Percentage of FinanceLeaseRightOfUseAsset	100.0	100.0	100.0	100.0	100.0

us-gaap:FinanceLeaseWeightedAverageDiscountRatePercent

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	0.076	0.0764	0.077	0.077	0.075
Percentage of FinanceLeaseWeightedAverageDiscountRatePercent	100.0	100.0	100.0	100.0	100.0

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization

Period End	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	2016-12-31
Value	3400000.0	13100000.0	12500000.0	12000000.0	10900000.0	10200000.0	9500000.0	8200000.0	7200000.0	6500000.0	4800000.0
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

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue

us-gaap:InterestRateSwap, us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31	2018-09-30	2017-12-31	2017-09-30	2017-06-30	2016-12-31
Value	1038000.0	659000.0	866000.0	1408000.0	5878000.0	8504000.0	5242000.0	3145000.0	2744000.0	3143000.0
Percentage of InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestRateSwap, us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2018-12-31	2018-09-30	2017-12-31	2017-09-30	2017-06-30	2016-12-31
Value	1038000.0	659000.0	5878000.0	8504000.0	5242000.0	3145000.0	2744000.0	3143000.0
Percentage of InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue

tnk:FreightForwardAgreements, us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2018-12-31
Value	165000.0	86000.0	57000.0
Percentage of InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue	100.0	100.0	100.0

tnk:FreightForwardAgreements, us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2018-12-31
Value	165000.0	86000.0	57000.0
Percentage of InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue	100.0	100.0	100.0

us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent

Period End	2020-06-30	2019-12-31	2018-12-31
Value	0.0	2980000.0	0.0
Percentage of LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent	0.0	100.0	0.0

us-gaap:LongtermDebtType

us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity

us-gaap:RevolvingCreditFacility

Period End	2020-06-30	2019-12-31
Value	485600000.0	371500000.0
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity	100.0	100.0

us-gaap:LongtermDebtType

us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity

us-gaap:RevolvingCreditFacility

Period End	2020-06-30	2019-12-31
Value	250600000.0	30400000.0
Percentage of LineOfCreditFacilityRemainingBorrowingCapacity	100.0	100.0

us-gaap:LongtermDebtWeightedAverageInterestRate

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2013-06-30	2012-12-31	2011-12-31
Value	0.03	0.037	0.042	0.044	0.046	0.043	0.044	0.035	0.03	0.029	0.024	0.024	0.023	0.016	0.014	0.011	0.0112	0.011	0.012	0.012	0.022
Percentage of LongtermDebtWeightedAverageInterestRate	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:PrepaidExpenseCurrent

Period End	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	2016-12-31	2016-09-30	2016-06-30	2015-12-31	2015-06-30	2014-12-31	2014-06-30	2013-12-31	2012-12-31
Value	12103000.0	10288000.0	14108000.0	10146000.0	34096000.0	22662000.0	21523000.0	18690000.0	15832000.0	16664000.0	15684000.0	20053000.0	22736000.0	24320000.0	13656000.0	8883000.0	12036000.0	10361000.0	9714000.0
Percentage of PrepaidExpenseCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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:PropertyPlantAndEquipmentNetExcludingCapitalLeasedAssets

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	1161097000.0	1223085000.0	1310541000.0	1327480000.0	1401551000.0
Percentage of PropertyPlantAndEquipmentNetExcludingCapitalLeasedAssets	100.0	100.0	100.0	100.0	100.0

us-gaap:LongLivedAssetsHeldForSaleByAssetType

us-gaap:RestrictedCashAndCashEquivalents

tnk:RestrictedCash

Period End	2020-06-30	2019-12-31	2019-06-30	2018-12-31
Value	0.0	337000.0	0.0	0.0
Percentage of RestrictedCashAndCashEquivalents	0.0	100.0	0.0	0.0

us-gaap:RestrictedCashCurrent

Period End	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	2016-12-31
Value	4766000.0	3071000.0	2341000.0	1916000.0	2153000.0	1794000.0	1858000.0	1599000.0	1645000.0	1380000.0	750000.0
Percentage of RestrictedCashCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RestrictedCashNoncurrent

Period End	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	2016-12-31
Value	3437000.0	3437000.0	3437000.0	3437000.0	3437000.0	2672000.0	2672000.0	2672000.0	2672000.0	0.0	0.0
Percentage of RestrictedCashNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0

us-gaap:SaleLeasebackTransactionAccumulatedDepreciation

Period End	2020-06-30	2019-12-31	2018-12-31
Value	159000000.0	143700000.0	111300000.0
Percentage of SaleLeasebackTransactionAccumulatedDepreciation	100.0	100.0	100.0

us-gaap:ShortTermBorrowings

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	10000000.0	50000000.0	50000000.0	15000000.0	0.0
Percentage of ShortTermBorrowings	100.0	100.0	100.0	100.0	0.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel2, us-gaap:CarryingReportedAmountFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31
Value	10000000.0	50000000.0	50000000.0	15000000.0	0.0
Percentage of ShortTermBorrowings	100.0	100.0	100.0	100.0	0.0

us-gaap:FairValueInputsLevel2, us-gaap:EstimateOfFairValueFairValueDisclosure, us-gaap:FairValueMeasurementsRecurring

Period End	2020-06-30	2019-12-31	2018-12-31
Value	9991000.0	50000000.0	0.0
Percentage of ShortTermBorrowings	99.9	100.0	0.0

Line plots across dimensions of each concept

us-gaap:CommonStockSharesIssued
us-gaap:StatementClassOfStock
(None,)

us-gaap:CommonStockSharesOutstanding
us-gaap:StatementClassOfStock
(None,)

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
('us-gaap:OperatingSegments', None)

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:ProductOrService
(None,)

us-gaap:OperatingCostsAndExpenses
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
('us-gaap:OperatingSegments', None)

us-gaap:GeneralAndAdministrativeExpense
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
('us-gaap:OperatingSegments', None)

us-gaap:OperatingIncomeLoss
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
('us-gaap:OperatingSegments', None)

Operating Margin
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
('us-gaap:OperatingSegments', None)

us-gaap:Assets
us-gaap:StatementBusinessSegments
(None,)

us-gaap:StockholdersEquity
us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents
(None, 'us-gaap:CommonStockIncludingAdditionalPaidInCapital')

us-gaap:StockholdersEquity
us-gaap:StatementClassOfStock, us-gaap:StatementEquityComponents
(None, 'us-gaap:CommonStockIncludingAdditionalPaidInCapital')