Derivative Instruments - Gain (Loss) for Derivative Instruments Not Designated or Qualifying as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Realized (losses) gains	$ 80	$ (181)	$ 559	$ (10,923)
Unrealized gains (losses)	310	3,810	(1,268)	3,021
Total	390	3,629	(709)	(7,902)
Interest rate swap agreements
Derivative [Line Items]
Realized (losses) gains	(154)	(1,277)	(894)	(12,145)
Unrealized gains (losses)	401	3,800	2	5,914
Total	247	2,523	(892)	(6,231)
Stock purchase warrant
Derivative [Line Items]
Realized (losses) gains	0	0	0	0
Unrealized gains (losses)	0	(199)	(287)	(4,447)
Total	0	(199)	(287)	(4,447)
Time-charter swap agreement
Derivative [Line Items]
Realized (losses) gains	0	1,096	1,106	1,222
Unrealized gains (losses)	0	209	(875)	1,554
Total	0	1,305	231	2,776
Forward freight agreements
Derivative [Line Items]
Realized (losses) gains	234	0	347	0
Unrealized gains (losses)	(91)	0	(108)	0
Total	$ 143	$ 0	$ 239	$ 0

Derivative instruments not designated as hedging instruments realized gain (loss) net.

No definition available.

Name:	tnk_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRealizedGainLossNet
Namespace Prefix:	tnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

Name:	us-gaap_UnrealizedGainLossOnDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_WarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=tnk_TimecharterSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=tnk_FreightForwardAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: