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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Realized gains (losses)	$ 592	$ 80	$ 1,438	$ 559
Unrealized gains (losses)	4	310	3,287	(1,268)
Total	596	390	4,725	(709)
Interest rate swap agreements
Derivative [Line Items]
Realized gains (losses)	711	(154)	1,575	(894)
Unrealized gains (losses)	13	401	3,262	2
Total	724	247	4,837	(892)
Stock purchase warrant
Derivative [Line Items]
Realized gains (losses)			0	0
Unrealized gains (losses)			0	(287)
Total			0	(287)
Time-charter swap agreement
Derivative [Line Items]
Realized gains (losses)			0	1,106
Unrealized gains (losses)			0	(875)
Total			0	231
Forward freight agreements
Derivative [Line Items]
Realized gains (losses)	(119)	234	(137)	347
Unrealized gains (losses)	(9)	(91)	25	(108)
Total	$ (128)	$ 143	$ (112)	$ 239

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: