Teekay Tankers (TNK) 6-K 30 Nov 18 2018 Q3 Current report (foreign) Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2018
Document And Entity Information [Abstract]
Document Type	6-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	TNK
Entity Registrant Name	TEEKAY TANKERS LTD.
Entity Central Index Key	1,419,945
Current Fiscal Year End Date	--12-31

Unaudited Consolidated Statemen

Unaudited Consolidated Statements of Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
REVENUES
Total revenues	$ 175,915	$ 91,238	$ 516,039	$ 330,512
Voyage expenses (notes 2, 3 and 13a)	(83,048)	(18,303)	(249,974)	(61,488)
Vessel operating expenses (note 13a)	(52,161)	(40,958)	(157,808)	(131,949)
Time-charter hire expense	(4,317)	(5,835)	(14,697)	(27,459)
Depreciation and amortization	(29,595)	(24,328)	(88,598)	(73,652)
General and administrative expenses (note 13a)	(8,747)	(7,622)	(27,939)	(24,875)
(Loss) gain on sale of vessels (note 14)	0	(7,926)	170	(12,495)
Restructuring charges	(213)	0	(1,195)	0
Loss from operations	(2,166)	(13,734)	(24,002)	(1,406)
Interest expense	(15,006)	(7,299)	(41,666)	(21,681)
Interest income	250	305	568	744
Realized and unrealized gain (loss) on derivative instruments (note 9)	596	390	4,725	(709)
Equity (loss) income (note 6)	(359)	(274)	265	(27,174)
Other expense (note 10)	(799)	(1,768)	(3,940)	(5,918)
Net loss	$ (17,484)	$ (22,380)	$ (64,050)	$ (56,144)
Per common share amounts (note 15)
- Basic (loss) earnings per share (usd per share)	$ (0.07)	$ (0.12)	$ (0.24)	$ (0.31)
- Diluted (loss) earnings per share (usd per share)	(0.07)	(0.12)	(0.24)	(0.31)
- Cash dividends declared (usd per share)	$ 0	$ 0.03	$ 0.03	$ 0.09
Weighted-average number of Class A and Class B common stock outstanding (note 15)
- Basic and Diluted (in shares)	268,558,556	179,224,094	268,470,804	178,853,698
Voyage charter revenues
REVENUES
Total revenues	$ 152,047	$ 25,397	$ 432,017	$ 94,881
Time-charter revenues
REVENUES
Total revenues	12,326	24,681	51,820	85,102
Other revenues
REVENUES
Total revenues	11,542	12,914	32,202	41,994
Net pool revenues
REVENUES
Total revenues	$ 0	$ 28,246	$ 0	$ 108,535

Unaudited Consolidated Balance

Unaudited Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current
Cash and cash equivalents	$ 54,361	$ 71,439
Restricted cash – current	1,794	1,599
Pool receivable from affiliates, net (note 13b)	26,923	15,550
Accounts receivable, including affiliate balances of $0.2 million (2017 - $0.8 million) (note 2)	17,048	19,288
Due from affiliates (note 13b)	50,551	49,103
Current portion of derivative assets (note 9)	3,075	1,016
Prepaid expenses	22,662	18,690
Other current assets (note 2)	1,385	0
Total current assets	177,799	176,685
Restricted cash – long-term	2,672	2,672
Vessels and equipment At cost, less accumulated depreciation of $550.1 million (2017 - $512.0 million) (note 7)	1,556,959	1,737,792
Vessels related to capital leases At cost, less accumulated depreciation of $38.7 million (2017 - $25.4 million) (note 8)	340,961	227,722
Investment in and advances to equity accounted investments (note 6)	24,811	25,460
Derivative assets (note 9)	5,531	4,226
Intangible assets At cost, less accumulated amortization of $10.2 million (2017 - $8.2 million)	12,320	14,605
Other non-current assets	82	127
Goodwill	8,059	8,059
Total assets	2,129,194	2,197,348
Current
Accounts payable	5,352	7,860
Accrued liabilities	35,717	34,608
Current portion of long-term debt (note 7)	103,843	166,745
Current obligation related to capital leases (note 8)	15,839	7,227
Deferred revenue	89	557
Due to affiliates (note 13b)	18,391	19,717
Total current liabilities	179,231	236,714
Long-term debt (note 7)	703,235	785,557
Long-term obligation related to capital leases (note 8)	280,871	141,681
Other long-term liabilities (note 10)	30,646	26,795
Total liabilities	1,193,983	1,190,747
Commitments and contingencies (notes 6, 7, 8 and 9)
Equity
Common stock and additional paid-in capital (585.0 million shares authorized, 231.6 million Class A and 37.0 million Class B shares issued and outstanding as of September 30, 2018 and 231.2 million Class A and 37.0 million Class B shares issued and outstanding as of December 31, 2017) (note 12)	1,295,709	1,294,998
Accumulated deficit	(360,498)	(288,397)
Total equity	935,211	1,006,601
Total liabilities and equity	$ 2,129,194	$ 2,197,348

Unaudited Consolidated Balanc_2

Unaudited Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts receivable, related parties, current	$ 0.2	$ 0.8
Accumulated depreciation on vessels and equipment	550.1	512
Accumulated depreciation on vessels related to capital leases	38.7	25.4
Accumulated amortization on intangible assets	$ 10.2	$ 8.2
Common stock, shares authorized (in shares)	585,000,000	385,000,000
Class A
Common stock, shares authorized (in shares)	485,000,000	285,000,000
Common stock, shares issued (in shares)	231,600,000	231,200,000
Common stock, shares outstanding (in shares)	231,600,000	231,200,000
Class B
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	37,000,000	37,000,000
Common stock, shares outstanding (in shares)	37,000,000	37,000,000

Unaudited Consolidated Statem_2

Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
OPERATING ACTIVITIES
Net loss	$ (64,050)	$ (56,144)
Non-cash items:
Depreciation and amortization	88,598	73,652
(Gain) loss on sale of vessels (note 14)	(170)	12,495
Unrealized (gain) loss on derivative instruments (note 9)	(3,287)	1,268
Equity (income) loss	(265)	27,174
Other	8,166	8,827
Change in operating assets and liabilities	(17,402)	7,013
Expenditures for dry docking	(17,035)	(6,448)
Net operating cash flow	(5,445)	67,837
FINANCING ACTIVITIES
Proceeds from long-term debt, net of issuance costs	46,128	14,919
Repayments of long-term debt	(92,380)	(82,054)
Prepayments of long-term debt	(102,717)	(222,302)
Proceeds from financing related to sales and leaseback of vessels (note 8)	156,644	153,000
Scheduled repayments of obligations related to capital leases (note 8)	(8,841)	(2,312)
Cash dividends paid	(8,052)	(15,302)
Proceeds from issuance of Class A common stock (note 12)	0	5,000
Proceeds from equity offerings, net of offering costs (note 12)	0	8,565
Other	(92)	(241)
Net financing cash flow	(9,310)	(140,727)
INVESTING ACTIVITIES
Proceeds from sales of vessels (note 14)	589	45,859
Expenditures for vessels and equipment	(3,463)	(3,503)
Return of capital from equity-accounted investment	746	0
Loan repayments from equity-accounted investment	0	550
Net investing cash flow	(2,128)	42,906
Decrease in cash, cash equivalents and restricted cash	(16,883)	(29,984)
Cash, cash equivalents and restricted cash, beginning of the period	75,710	94,907
Cash, cash equivalents and restricted cash, end of the period	$ 58,827	$ 64,923

Unaudited Consolidated Statem_3

Unaudited Consolidated Statement of Changes in Equity - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock and Additional Paid-in Capital	Common Stock and Additional Paid-in CapitalClass A	Common Stock and Additional Paid-in CapitalClass B	Accumulated Deficit
Balance at beginning of period (shares) at Dec. 31, 2017		268,202
Balance at beginning of period at Dec. 31, 2017	$ 1,006,601		$ 1,206,466	$ 88,532	$ (288,397)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(64,050)				(64,050)
Dividends declared	(8,052)				(8,052)
Equity-based compensation (note 12) (in shares)		357
Equity-based compensation (note 12)	985		985
Other	(273)		(274)		1
Balance at end of period (shares) at Sep. 30, 2018		268,559
Balance at end of period at Sep. 30, 2018	$ 935,211		$ 1,207,177	$ 88,532	$ (360,498)

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited interim consolidated financial statements (or consolidated financial statements ) have been prepared in conformity with United States generally accepted accounting principles (or GAAP ). These consolidated financial statements include the accounts of Teekay Tankers Ltd., its wholly-owned subsidiaries, equity-accounted investments, the Entities under Common Control (as defined in note 4 ) and any variable interest entities (or VIEs ) of which it is the primary beneficiary (collectively, the Company ). The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Certain information and footnote disclosures required by GAAP for complete annual financial statements have been omitted and, therefore, these consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements for the year ended December 31, 2017 , filed on Form 20-F with the U.S. Securities and Exchange Commission (or the SEC ) on April 24, 2018. In the opinion of management, these consolidated financial statements reflect all adjustments, consisting solely of a normal recurring nature, necessary to present fairly, in all material respects, the Company’s consolidated financial position, results of operations, and cash flows for the interim periods presented. The results of operations for the interim periods presented are not necessarily indicative of those for a full fiscal year. Significant intercompany balances and transactions have been eliminated upon consolidation.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2018
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (or FASB ) issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers , (or ASU 2014-09 ). ASU 2014-09 requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This update creates a five-step model that requires entities to exercise judgment when considering the terms of the contract(s) which include (i) identifying the contract(s) with the customer, (ii) identifying the separate performance obligations in the contract, (iii) determining the transaction price, (iv) allocating the transaction price to the separate performance obligations, and (v) recognizing revenue as each performance obligation is satisfied. ASU 2014-09 became effective for the Company as of January 1, 2018 and may be applied, at the Company’s option, retrospectively to each period presented or as a cumulative-effect adjustment as of such date. The Company has elected to apply ASU 2014-09 only to those contracts that were not completed as of January 1, 2018. The Company has adopted ASU 2014-09 as a cumulative-effect adjustment as of the date of adoption. The Company has identified the following differences on adoption of ASU 2014-09: • The Company previously presented the net allocation for its vessels participating in revenue sharing arrangements (or RSAs ) as net pool revenues. The Company has determined that it is the principal in voyages its vessels perform that are included in the RSAs. As such, the revenue from those voyages is presented in voyage charter revenues and the difference between this amount and the Company's net allocation from the RSA is presented as voyage expenses. This had the effect of increasing voyage charter revenues and voyage expenses for the three and nine months ended September 30, 2018 by $73.6 million and $202.4 million , respectively. There was no cumulative impact to opening equity as at January 1, 2018. • The Company previously presented all accrued revenue as a component of accounts receivable. The Company has determined that if the right to such consideration is conditioned upon something other than the passage of time, such accrued revenue should be presented apart from accounts receivable. This had the effect of increasing other current assets and decreasing accounts receivable by $1.4 million at September 30, 2018 . In February 2016, FASB issued Accounting Standards Update 2016-02, Leases (or ASU 2016-02 ). ASU 2016-02 establishes a right-of-use model that requires a lessee to record a right-of-use asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. For lessees, leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. ASU 2016-02 requires lessors to classify leases as a sales-type, direct financing, or operating lease. A lease is a sales-type lease if any one of five criteria are met, each of which indicate that the lease, in effect, transfers control of the underlying asset to the lessee. If none of those five criteria are met, but two additional criteria are both met, indicating that the lessor has transferred substantially all of the risks and benefits of the underlying asset to the lessee and a third party, the lease is a direct financing lease. All leases that are not sales-type leases or direct financing leases are operating leases. ASU 2016-02 is effective January 1, 2019, with early adoption permitted. FASB issued an additional accounting standards update in July 2018 that made further amendments to accounting for leases, including allowing the use of a transition approach whereby a cumulative effect adjustment is made as of the effective date, with no retrospective effect. The Company has elected to use this new optional transition approach. The Company will adopt ASU 2016-02 on January 1, 2019. To determine the cumulative effect adjustment, the Company will not reassess lease classification, initial direct costs for any existing leases and whether any expired or existing contracts are or contain leases. The adoption of ASU 2016-02 will result in a change in a ccounting method for the lease portion of the daily charter hire for the Company’s chartered-in vessels accounted for as operating leases with firm periods of greater than one year. Under ASU 2016-02, the Company will recognize a right-of-use asset and a lease liability on the balance sheet for these charters based on the present value of future minimum lease payments, whereas currently no right-of-use asset or lease liability is recognized. This will have the result of increasing the Company’s assets and liabilities. The pattern of expense recognition of chartered-in vessels is expected to remain substantially unchanged, unless the right-of-use asset becomes impaired. The Company is expecting to disclose in its consolidated financial statements for the year ended December 31, 2018 the quantitative impact of adopting ASU 2016-02. In June 2016, the FASB issued Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments . This update replaces the incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. This update is effective for the Company as of January 1, 2020, with a modified-retrospective approach. The Company is currently evaluating the effect of adopting this new guidance. In August 2016, the FASB issued Accounting Standards Update 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments , which, among other things, provides guidance on two acceptable approaches of classifying distributions received from equity method investees in the statement of cash flows. This update became effective for the Company as of January 1, 2018, with a retrospective approach. The Company has elected to classify distributions received from equity method investees in the statement of cash flows based on the nature of the distribution. The adoption of this update did not have a material impact on the Company. In November 2016, the FASB issued Accounting Standards Update 2016-18, Statement of Cash Flows: Restricted Cash , (or ASU 2016-18 ). ASU 2016-18 requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Entities are also required to reconcile such total to amounts on the balance sheet and disclose the nature of the restrictions. ASU 2016-18 became effective for the Company as of January 1, 2018. Adoption of ASU 2016-18 resulted in the Company including in its statement of cash flows changes in cash, cash equivalents and restricted cash.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue The Company’s primary source of revenue is from chartering its vessels (Aframax tankers, Suezmax tankers and Long Range 2 (or LR2 ) tankers) to its customers. The Company utilizes two primary forms of contracts, consisting of voyage charters and time-charters. The extent to which the Company employs its vessels on voyage charters versus time charters is dependent upon the Company’s chartering strategy and the availability of time charters. Spot market rates for voyage charters, including conventional voyages and lightering voyages, are volatile from period to period, whereas time charters provide a stable source of monthly revenue. The Company also provides ship-to-ship support services, which includes managing the process of transferring cargo between seagoing ships positioned alongside each other, either stationary or underway, as well as commercial management services to third-party owners of vessels. Finally, the Company manages LNG terminals and procures LNG-related goods and services for terminal owners and other customers. Voyage Charters Voyage charters are charters for a specific voyage that are usually priced on a current or "spot" market rate and then adjusted for any pool participation based on predetermined criteria. Voyage charters for full service lightering voyages may also be priced based on pre-agreed terms. The performance obligations within a voyage charter contract, which will typically include the lease of the vessel to the charterer as well as the operation of the vessel, are satisfied as services are rendered over the duration of the voyage, as measured using the time that has elapsed from commencement of performance. In addition, any expenses that are unique to a particular voyage, including bunker fuel expenses, port fees, cargo loading and unloading expenses, canal tolls, agency fees and commissions, are the responsibility of the vessel owner. The Company’s voyage charters will normally contain a lease; however, judgment is necessary to determine whether this is the case based upon the decision-making rights the charterer has under the contract. Such contracts are considered either fixed or variable, depending on certain conditions. Delays caused by the charterer result in additional consideration. Payment for the voyage is not due until the voyage is completed. The duration of a single voyage will typically be less than three months. The Company does not engage in any specific tactics to minimize vessel residual value risk due to the short-term nature of the contracts. Time Charters Pursuant to a time charter, the Company charters a vessel to a customer for a fixed period of time, generally one year or more. The performance obligations within a time-charter contract, which will include the lease of the vessel to the charterer as well as the operation of the vessel, are satisfied as services are rendered over the duration of such contract, as measured using the time that has elapsed from commencement of performance. In addition, any expenses that are unique to a particular voyage, including any bunker fuel expenses, port fees, cargo loading and unloading expenses, canal tolls, agency fees and commissions, are the responsibility of the customer, as long as the vessel is not off-hire. Hire is typically invoiced monthly in advance for time-charter contracts, based on a fixed daily hire amount. However, certain sources of variability exist, including off-hire and profit share revenue. If the vessel is off-hire due to mechanical breakdown or for any other reason, the charterer does not pay charter hire for this time. For contracts including a profit share component, the profit share consideration occurs when actual spot tanker rates earned by the vessel exceed certain thresholds for a period of time. During the three and nine months ended September 30, 2018 , the Company’s share of the revenue from the vessel in the Company’s High-Q Investment Ltd. (or High-Q ) joint venture was $0.7 million and $3.4 million , respectively ( September 30, 2017 - $1.7 million and $5.1 million ). Variable consideration of the Company’s contracts is typically recognized as incurred, as either such revenue is allocated and accounted for under lease accounting requirements or, alternatively, such consideration is allocated to distinct periods within a contract that such variable consideration was incurred in. The Company does not engage in any specific tactics to minimize vessel residual value risk. As at September 30, 2018 , six of the Company’s vessels operated under time-charter contracts with the Company’s customers, of which four contracts are scheduled to expire in in the fourth quarter of 2018, and two contracts are scheduled to expire in 2019. One of the Company’s vessels is employed on a time-charter contract whereby the charterer has the option to extend the charter by one period of 12 months. As at September 30, 2018 , the future hire payments to be received by the Company under time charters then in place were approximately $14.4 million , comprised of $8.1 million (remaining 2018) and $6.3 million (2019). The hire payments should not be construed to reflect a forecast of total charter hire revenues for any of the periods. Future hire payments do not include hire payments generated from new contracts entered into after September 30, 2018 , from unexercised option periods of contracts that existed on September 30, 2018 or from variable consideration, if any. In addition, future hire payments presented above have been reduced by estimated off-hire time for required period maintenance. Actual amounts may vary given future events such as unplanned vessel maintenance. The carrying amount of the Company's owned vessels employed on time charters as at September 30, 2018 , was $196.8 million (December 31, 2017 - $517.9 million ). The cost and accumulated depreciation of the vessels employed on these time charters as at September 30, 2018 were $303.8 million (December 31, 2017 - $754.2 million ) and $107.0 million (December 31, 2017 - $236.3 million ), respectively. As at September 30, 2018 , the Company had $0.1 million (December 31, 2017 - $0.5 million ) of advanced payments recognized as contract liabilities that are expected to be recognized as time-charter revenues in the following period and are included in deferred revenue on the Company's consolidated balance sheets. Other Revenues Ship-to-ship support services include managing the process of transferring cargo between seagoing ships positioned alongside each other. Each operation is typically completed in less than 48 hours. The performance obligations within a commercial management contract are satisfied as services are rendered over the duration of such contracts. The management fee, consisting of a fixed component based on the number of days a vessel was under management and a variable component based on the vessel’s monthly earnings, is invoiced monthly in arrears for commercial management contracts. The performance obligations within an LNG terminal contract are satisfied as services are rendered over the duration of such contracts. The management fee, consisting of a fixed amount, subject to contingent annual inflationary adjustments, is typically invoiced monthly in arrears. Substantially all of the Company’s performance obligations are satisfied over the duration of the associated contract, and the Company uses the proportion of elapsed time as its method to recognize revenue over the contract duration. The variable consideration of the Company’s contracts is typically recognized as incurred as such consideration is allocated to distinct periods within a contract that such variable consideration was incurred in. Revenue Table The following table contains a breakdown of the Company's revenue by contract type for the three and nine months ended September 30, 2018 and September 30, 2017 . All revenue is part of the Company's conventional tanker segment, except for revenue for ship-to-ship support services and LNG terminal management, consultancy, procurement and other related services, which is part of the Company's ship-to-ship transfer segment. Three Months Ended Three Months Ended Nine Months Ended Nine Months Ended Voyage charters (1) Suezmax 90,267 271 243,771 12,905 Aframax 29,210 4,869 76,952 13,900 LR2 16,712 — 40,312 — Full service lightering 15,858 20,257 70,982 68,076 Total 152,047 25,397 432,017 94,881 Time-charters Aframax 7,784 12,318 31,608 36,975 Suezmax 2,909 9,167 13,063 35,918 LR2 1,633 3,196 7,149 12,209 Total 12,326 24,681 51,820 85,102 Other revenue Ship-to-ship support services 8,217 7,980 22,452 28,210 Commercial management 2,050 3,112 6,246 9,448 LNG terminal management, consultancy and other 1,275 1,822 3,504 4,336 Total 11,542 12,914 32,202 41,994 Net pool revenues (1) Suezmax — 18,820 — 66,261 Aframax — 4,832 — 23,195 LR2 — 4,598 — 19,067 MR — (4 ) — 12 Total — 28,246 — 108,535 Total revenues 175,915 91,238 516,039 330,512 (1) Prior to the January 1, 2018 adoption of ASU 2014-09, the Company presented the net allocation for its vessels participating in RSAs as net pool revenues. The Company has determined that it is the principal in voyages its vessels perform that are included in the RSAs. As such, the revenue from those voyages is presented in voyage charter revenues and the difference between this amount and the Company's net allocation from the RSA is presented as voyage expenses. The adoption of ASU 2014-09 had the impact of increasing voyage charter revenues and voyage expenses for the three and nine months ended September 30, 2018 by $73.6 million and $202.4 million , respectively.

Acquisition of Entities under C

Acquisition of Entities under Common Control	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisition of Entities under Common Control	Acquisition of Entities under Common Control On May 31, 2017, the Company acquired from Teekay Holdings Ltd., a wholly-owned subsidiary of Teekay Corporation (or Teekay ), the remaining 50% interest in Teekay Tanker Operations Ltd. (or TTOL ) (see also note 6 c) for $39.0 million , which included $13.1 million for working capital assumed. The Company issued approximately 13.8 million shares of the Company's Class B common stock to Teekay as consideration in addition to the working capital consideration of $13.1 million . As a result of the acquisition of a controlling interest in TTOL, the Company's consolidated financial statements prior to the date the Company acquired a controlling interest in TTOL are retroactively adjusted to eliminate the equity method of accounting previously used for the original 50% interest owned and to include 100% of the assets and liabilities and results of TTOL on a consolidated basis during the periods TTOL and the Company were under common control of Teekay and had begun operations. The effect of adjusting such information to accounts in periods prior to the Company's acquisition of the remaining 50% thereof is referred to as the "Entities under Common Control." All intercorporate transactions between the Company and TTOL that occurred prior to the acquisition by the Company have been eliminated upon consolidation. Assets and liabilities of TTOL are reflected on the Company’s consolidated balance sheets at TTOL’s historical carrying values. The amount of the net consideration of $39.0 million that was in excess of TTOL’s historical carrying value of the net assets acquired of $13.3 million has been accounted for as a $25.7 million return of capital to Teekay. The effect of adjusting the Company’s consolidated financial statements for the TTOL common control transaction decreased the Company's net loss for the nine months ended September 30, 2017 by $1.3 million and increased the Company's revenues for the nine months ended September 30, 2017 by $8.6 million .

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company has two reportable segments, its conventional tanker segment and its ship-to-ship transfer segment. The Company’s conventional tanker segment consists of the operation of all of its tankers, including the operations of TTOL and Tanker Investments Ltd. (or TIL ), which were acquired in 2017 (notes 4 , 6 and 18), and those tankers employed on full service lightering contracts. The Company’s ship-to-ship transfer segment consists of the Company’s lightering support services, including those provided to the Company’s conventional tanker segment as part of full service lightering operations and LNG terminal management, consultancy, procurement and other related services. Segment results are evaluated based on income from operations. The accounting policies applied to the reportable segments are the same as those used in the preparation of the Company’s consolidated financial statements. The following tables include results for the Company’s revenues and (loss) income from operations by segment for the three and nine months ended September 30, 2018 and September 30, 2017 . Three Months Ended September 30, 2018 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 166,423 12,019 (2,527 ) 175,915 Voyage expenses (3) (85,575 ) — 2,527 (83,048 ) Vessel operating expenses (43,432 ) (8,729 ) — (52,161 ) Time-charter hire expense (2,935 ) (1,382 ) — (4,317 ) Depreciation and amortization (28,532 ) (1,063 ) — (29,595 ) General and administrative expenses (4) (7,985 ) (762 ) — (8,747 ) Restructuring charges — (213 ) — (213 ) Loss from operations (2,036 ) (130 ) — (2,166 ) Equity loss (359 ) — — (359 ) Three Months Ended September 30, 2017 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 81,758 11,902 (2,422 ) 91,238 Voyage expenses (3) (20,725 ) — 2,422 (18,303 ) Vessel operating expenses (32,227 ) (8,731 ) — (40,958 ) Time-charter hire expense (4,629 ) (1,206 ) — (5,835 ) Depreciation and amortization (23,071 ) (1,257 ) — (24,328 ) General and administrative expenses (4) (6,823 ) (799 ) — (7,622 ) (Loss) gain on sale of vessels (7,968 ) 42 — (7,926 ) Loss from operations (13,685 ) (49 ) — (13,734 ) Equity loss (274 ) — — (274 ) Nine Months Ended September 30, 2018 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 490,083 35,061 (9,105 ) 516,039 Voyage expenses (3) (259,079 ) — 9,105 (249,974 ) Vessel operating expenses (131,886 ) (25,922 ) — (157,808 ) Time-charter hire expense (10,326 ) (4,371 ) — (14,697 ) Depreciation and amortization (85,171 ) (3,427 ) — (88,598 ) General and administrative expenses (4) (25,385 ) (2,554 ) — (27,939 ) Gain on sale of vessels — 170 — 170 Restructuring charges (152 ) (1,043 ) — (1,195 ) Loss from operations (21,916 ) (2,086 ) — (24,002 ) Equity income 265 — — 265 Nine months ended September 30, 2017 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 299,154 39,387 (8,029 ) 330,512 Voyage expenses (3) (69,517 ) — 8,029 (61,488 ) Vessel operating expenses (100,586 ) (31,363 ) — (131,949 ) Time-charter hire expense (23,698 ) (3,761 ) — (27,459 ) Depreciation and amortization (69,857 ) (3,795 ) — (73,652 ) General and administrative expenses (4) (22,258 ) (2,617 ) — (24,875 ) (Loss) gain on sale of vessels (12,545 ) 50 — (12,495 ) Income (loss) from operations 693 (2,099 ) — (1,406 ) Equity loss (27,174 ) — — (27,174 ) (1) The ship-to-ship transfer segment provides lightering support services to the conventional tanker segment for full service lightering operations and the pricing for such services was based on actual costs incurred. (2) Revenues, net of the inter-segment adjustment, earned from the ship-to-ship transfer segment are reflected in Other Revenues in the Company's consolidated statements of loss. (3) The comparative periods do not include the impact of the January 1, 2018 adoption of ASU 2014-09 (see note 2). (4) Includes direct general and administrative expenses and indirect general and administrative expenses (allocated to each segment based on estimated use of corporate resources). A reconciliation of total segment assets to total assets presented in the accompanying consolidated balance sheets is as follows: As at As at September 30, 2018 December 31, 2017 $ $ Conventional Tanker Segment 2,036,698 2,089,099 Ship-to-Ship Transfer Segment 38,135 36,810 Cash and cash equivalents 54,361 71,439 Consolidated total assets 2,129,194 2,197,348

Investments in and Advances to

Investments in and Advances to Equity Accounted Investments	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in and Advances to Equity Accounted Investments	Investments in and Advances to Equity-Accounted Investments As at September 30, 2018 As at December 31, 2017 $ $ High-Q Joint Venture 24,811 24,546 Gemini Tankers L.L.C. — 914 Total 24,811 25,460 a. The Company has a joint venture arrangement with Wah Kwong Maritime Transport Holdings Limited (or Wah Kwong ), whereby the Company has a 50% economic interest in the High-Q joint venture, which is jointly controlled by the Company and Wah Kwong. The High-Q joint venture owns one Very Large Crude Carrier (or VLCC ), which traded on a fixed time charter-out contract that expired in May 2018. Under the fixed contract, the vessel earned a daily rate and an additional amount if the daily rate of sub-charters exceeded a certain threshold. The VLCC completed its dry dock in July 2018 and subsequently began trading on spot voyage charters in a pooling arrangement managed by a third party. As at September 30, 2018 , the High-Q joint venture has a loan outstanding with a financial institution with a balance of $38.7 million ( December 31, 2017 – $42.7 million ). The loan is secured by a first-priority mortgage on the VLCC owned by the High-Q joint venture and 50% of the outstanding loan balance is guaranteed by the Company. The High-Q joint venture also had an interest rate swap agreement that expired in June 2018. The interest rate swap exchanged a receipt of floating interest based on 3-months LIBOR for a payment of a fixed rate of 1.47% every three months. b. In January 2014, the Company and Teekay formed TIL, which owned and operated conventional tankers. The Company purchased 2.5 million shares of TIL common stock for $25.0 million and received a stock purchase warrant entitling it to purchase up to 750,000 additional shares of common stock of TIL (note 9 ). The Company also received one preferred share which entitled the Company to elect one board member of TIL. The preferred share did not give the Company a right to any dividends or distributions of TIL. On May 31, 2017, the Company entered into a Merger Agreement to acquire the remaining 27.0 million issued and outstanding common shares of TIL, by way of a share-for-share exchange of 3.3 shares of Class A common stock of the Company for each outstanding share of TIL common stock not owned by the Company. Prior to the completion of the merger, the Company accounted for its 11.3% investment in TIL using the equity method. As the Company then accounted for its investment in TIL under the equity method, the Company was required to remeasure its previously held equity investment to fair value at the acquisition date. Based on the then pending transaction, the Company recognized an other than temporary impairment and remeasured its investment in TIL to fair value during the second quarter of 2017 based on the TIL share price at June 30, 2017, resulting in a write-down of $28.1 million presented in equity (loss) income on the consolidated statements of loss. On November 27, 2017, the Company completed the merger with TIL and the Company remeasured its equity investment in TIL to fair value based on the relative share exchange value at the date of the acquisition, which resulted in the recognition of a gain of $1.4 million presented in equity (loss) income on the consolidated statements of loss. c. On May 31, 2017, the Company purchased from Teekay the remaining 50% interest in TTOL, which owns conventional tanker commercial management and technical management operations and directly administers four commercially managed RSAs, for $39.0 million , which included $13.1 million for assumed working capital (note 4). Prior to the May 31, 2017 purchase, the Company equity-accounted for its initial 50% interest in TTOL.

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt As at As at September 30, 2018 December 31, 2017 $ $ Revolving Credit Facilities due through 2022 465,763 539,735 Term Loans due through 2021 348,946 423,512 Total principal 814,709 963,247 Less: unamortized discount and debt issuance costs (7,631 ) (10,945 ) Total debt 807,078 952,302 Less: current portion (103,843 ) (166,745 ) Non-current portion of long-term debt 703,235 785,557 As at September 30, 2018 , the Company had three revolving credit facilities (or the Revolvers ), which, as at such date, provided for aggregate borrowings of up to $500.6 million , of which $34.8 million was undrawn ( December 31, 2017 - $628.3 million , of which $88.6 million was undrawn). Interest payments are based on LIBOR plus margins. As at September 30, 2018 , such margins ranged between 2.00% and 2.75% ( December 31, 2017 : 0.45% and 2.75% ). The total amount available under the Revolvers reduces by $51.4 million (remainder of 2018), $19.2 million (2019), $19.2 million (2020), $311.9 million (2021) and $98.9 million (2022). As at September 30, 2018 , the Company also had three term loans outstanding, which totaled $348.9 million ( December 31, 2017 - $423.5 million ). Interest payments on the term loans are based on a combination of a fixed rate of 5.4% ( December 31, 2017 - 5.4% ) and variable rates based on LIBOR plus margins. As at September 30, 2018 , the margins ranged from 0.30% to 2.00% ( December 31, 2017 - 0.30% to 2.00% ). The term loan repayments are made in quarterly or semi-annual payments. Two of the term loans also have a balloon or bullet repayment due at maturity in 2021. These revolving credit facilities and term loans are further described below. In December 2017, the Company entered into a $270.0 million long-term debt facility (or the 2017 Revolver ), which is scheduled to mature in December 2022. In December 2017, $215.8 million of the 2017 Revolver was used to refinance two of the Company's debt facilities that were assumed in the merger with TIL (note 18). These debt facilities were scheduled to mature in April 2019 and June 2020. As at September 30, 2018 , the 2017 Revolver is collateralized by 8 of the Company's vessels, together with other related security. The 2017 Revolver also requires that the Company maintain a minimum hull coverage ratio of 125% of the total outstanding drawn balance for the facility period. Such requirement is assessed on a semi-annual basis with reference to vessel valuations compiled by two or more agreed upon third parties. Should the ratio drop below the required amount, the lender may request that the Company either prepay a portion of the loan in the amount of the shortfall or provide additional collateral in the amount of the shortfall, at the Company's option. As of September 30, 2018 , the hull coverage ratio was 174% ( December 31, 2017 - 191% ). The vessel values used in this ratio are appraised values provided by third parties where available or prepared by the Company based on second-hand sale and purchase market data. A decline in the tanker market could negatively affect the ratio. In addition, the Company is required to maintain a minimum liquidity (cash, cash equivalents and undrawn committed revolving credit lines with at least six months to maturity) of $35.0 million and at least 5% of the Company's total consolidated debt. The Company entered into a $894.4 million long-term debt facility (or the 2016 Debt Facility ), consisting of both a term loan and a revolving credit component, which are scheduled to mature in January 2021. The 2016 Debt Facility is collateralized by 29 of the Company’s vessels, together with other related security. The 2016 Debt Facility also requires that the Company maintain a minimum hull coverage ratio of 125% of the total outstanding drawn balance for the facility period. Such requirement is assessed on a semi-annual basis with reference to vessel valuations compiled by one or more agreed upon third parties. Should the ratio drop below the required amount, the lender may request that the Company either prepay a portion of the loan in the amount of the shortfall or provide additional collateral in the amount of the shortfall, at the Company’s option. As at September 30, 2018 , the hull coverage ratio was 134% ( December 31, 2017 - 145% ). The vessel values used in this ratio are appraised values provided by third parties where available or prepared by the Company based on second-hand sale and purchase market data. A decline in the tanker market could negatively affect the ratio. In addition, the Company is required to maintain a minimum liquidity (cash, cash equivalents and undrawn committed revolving credit lines with at least six months to maturity) of $35.0 million and at least 5.0% of the Company’s total consolidated debt. As at September 30, 2018 , the Company’s remaining revolver had an outstanding balance of $47.6 million (December 31, 2017 - $65.6 million ) and was scheduled to mature in November 2018. The revolver is collateralized by three of the Company’s vessels, together with other related security, and requires that the Company's applicable subsidiary maintain a minimum hull coverage ratio of 105% of the total outstanding drawn balance for the facility period. Such requirement is assessed on an annual basis, with reference to vessel valuations compiled by one or more agreed upon third parties. Should the ratio drop below the required amount, the lender may request the Company to either prepay a portion of the loan in the amount of the shortfall or provide additional collateral in the amount of the shortfall, at the Company’s option. As at September 30, 2018 , such revolver, with a minimum hull coverage ratio requirement, had a hull coverage ratio of 150% ( December 31, 2017 - 118% ). The vessel values used in this ratio are appraised values provided by third parties where available or prepared by the Company based on second-hand sale and purchase market data. A decline in the tanker market could negatively affect the ratio. The revolver is also guaranteed by Teekay and contains covenants that require Teekay (excluding the Company and Teekay LNG Partners L.P. (or TGP )) to maintain the greater of free liquidity (cash and cash equivalents and undrawn committed revolving credit lines with at least six months to maturity) of $50.0 million and at least 5.0% of Teekay’s total consolidated debt which has recourse to Teekay. The Company’s remaining two term loans are guaranteed by Teekay and are collateralized by six of the Company’s vessels, together with other related security. One of the term loans contains covenants that require Teekay and the Company collectively to maintain the greater of (a) free cash (cash and cash equivalents) of at least $50.0 million and (b) an aggregate of free cash and undrawn committed revolving credit lines with at least six months to maturity of at least 5.0% of Teekay’s total consolidated debt (excluding the debt of TGP). The other term loan requires Teekay and the Company collectively to maintain the greater of (a) free cash (cash and cash equivalents) of at least $100.0 million and (b) an aggregate of free cash and undrawn committed revolving credit lines with at least six months to maturity of at least 7.5% of Teekay's total consolidated debt (excluding the debt of TGP). As at September 30, 2018 , the Company was in compliance with all covenants in respect of the Revolvers and term loans. Teekay has also advised the Company that Teekay is in compliance with all covenants relating to the revolving credit facilities and term loans to which the Company is a party. The weighted-average interest rate on the Company’s long-term debt as at September 30, 2018 was 4.3% ( December 31, 2017 - 3.5% ). This rate does not reflect the effect of the Company’s interest rate swap agreements (note 9 ). The aggregate annual long-term principal repayments required to be made by the Company under the Revolvers and term loans subsequent to September 30, 2018 , including the effect of the sale-leaseback transaction described in note 20, are $25.9 million (remaining 2018), $104.6 million (2019), $120.9 million (2020), $426.8 million (2021), $102.5 million (2022) and $34.0 million (thereafter).

Leases

Leases	9 Months Ended
	Sep. 30, 2018
Leases [Abstract]
Leases	Leases Obligations Related to Capital Leases As at As at September 30, 2018 December 31, 2017 $ $ Aframax tankers 153,140 — Suezmax tankers 143,570 148,908 Total obligations related to capital leases 296,710 148,908 Less: current portion (15,839 ) (7,227 ) Long-term obligations related to capital leases 280,871 141,681 In September 2018, the Company completed a $156.6 million sale-leaseback financing transaction with a financial institution relating to six of the Company's Aframax tankers, the Blackcomb Spirit, Emerald Spirit, Garibaldi Spirit, Peak Spirit, Tarbet Spirit and Whistler Spirit . In July 2017, the Company also completed a $153.0 million sale-leaseback financing transaction with a financial institution relating to four of the Company's Suezmax tankers, the Athens Spirit , Beijing Spirit , Moscow Spirit and Sydney Spirit . Under these arrangements, the Company transferred the vessels to subsidiaries of the financial institutions (or collectively, the Lessors ) and leased the vessels back from the Lessors on bareboat charters ranging from nine to 12 -year terms. The Company has the option to purchase each of the four Suezmax tankers at any point between July 2020 and July 2029. The Company also has the option to purchase each of the six Aframax tankers at any point between September 2020 and the end of its respective term and is obligated to purchase the vessels on maturity of the bareboat charters. The Company understands that these vessels and lease operations are the only assets and operations of the Lessors. The Company operates the vessels during the lease term, and as a result, is considered to be the Lessors' primary beneficiary and therefore the Company consolidates the Lessors for financial reporting purposes. The liabilities of the Lessors are loans and are non-recourse to the Company. The amounts funded to the Lessors in order to purchase the vessels materially match the funding to be paid by the Company's subsidiaries under these lease-back transactions. As a result, the amounts due by the Company's subsidiaries to the Lessors have been included in obligations related to capital leases as representing the Lessors' loans. The bareboat charters related to these vessels require that the Company maintain a minimum liquidity (cash, cash equivalents and undrawn committed revolving credit lines with at least six months to maturity) of $35.0 million and at least 5.0% of the Company's consolidated debt and obligations related to capital leases (excluding applicable security deposits reflected in restricted cash - long-term on the Company's consolidated balance sheets). The Company is required for each of the four Suezmax tankers to maintain a hull coverage ratio of 90% of the total outstanding principal balance during the first three years of the lease period and 100% of the total outstanding principal balance thereafter. In addition, the Company is required for each of the six Aframax tankers to maintain a hull coverage ratio of 75% of the total outstanding principal balance during the first year of the lease period, 78% for the second year, 80% for the following two years and 90% of the total outstanding principal balance thereafter. Such requirement is assessed annually with reference to vessel valuations compiled by one or more agreed upon third parties. As at September 30, 2018 , this ratio for the Suezmax and Aframax tankers was approximately 100% and 89% , respectively (December 31, 2017 - 105% and nil ). As at September 30, 2018 , the Company was in compliance with all covenants in respect of the obligations related to capital leases. As at September 30, 2018 , the Company's remaining commitments under the 10 capital leases for the Suezmax and Aframax tankers was approximately $445.3 million , including imputed interest of $148.6 million , repayable from 2018 through 2029, as indicated below, excluding the sale-leaseback transaction described in note 20: Year Commitment Remaining 2018 $ 9,574 2019 $ 37,954 2020 $ 38,052 2021 $ 37,943 2022 $ 37,936 Thereafter $ 283,836

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments Interest rate swap agreements The Company uses derivatives in accordance with its overall risk management policies. The Company enters into interest rate swap agreements which exchange a receipt of floating interest for a payment of fixed interest to reduce the Company’s exposure to interest rate variability on its outstanding floating-rate debt. The Company has not designated, for accounting purposes, its interest rate swaps as cash flow hedges of its U.S. Dollar LIBOR-denominated borrowings. As at September 30, 2018 , the Company was committed to the following interest rate swap agreements: Interest Rate Notional Amount Fair Value / Carrying Amount of Asset Remaining Term Fixed Interest Rate Index $ $ (years) (%) (1) LIBOR-Based Debt: U.S. Dollar-denominated interest rate swaps (2) LIBOR 104,133 1,770 2.3 1.46 U.S. Dollar-denominated interest rate swaps LIBOR 150,000 4,720 2.3 1.55 U.S. Dollar-denominated interest rate swaps LIBOR 50,000 2,014 2.3 1.16 (1) Excludes the margin the Company pays on its variable-rate debt, which, as of September 30, 2018 , ranged from 0.30% to 2.75% . (2) Notional amount reduces quarterly. The Company is potentially exposed to credit loss in the event of non-performance by the counterparty to the interest rate swap agreements in the event that the fair value results in an asset being recorded. In order to minimize counterparty risk, the Company only enters into interest rate swap agreements with counterparties that are rated A– or better by Standard & Poor’s or A3 or better by Moody’s at the time transactions are entered into. Stock purchase warrant During 2017, the Company had one stock purchase warrant, which had entitled it to purchase up to 750,000 shares of common stock of TIL at certain conditions at pre-determined prices. The stock purchase warrant was not exercised and was canceled upon completion of the TIL merger in November 2017 (notes 6 and 18). Time-charter swap agreement Effective June 1, 2016, the Company entered into a time-charter swap agreement for 55% of two Aframax equivalent vessels. Under such agreement, the Company received $27,776 per day, less a 1.25% brokerage commission, and paid 55% of the net revenue distribution of two Aframax equivalent vessels employed in the Company’s Aframax RSA, less $500 per day, for a period of 11 months plus an additional two months at the counterparty’s option. The purpose of the agreement was to reduce the Company’s exposure to spot tanker market rate variability for certain of its vessels that are employed in the Aframax RSA. The Company did not designate, for accounting purposes, the time-charter swap as a cash flow hedge. As of May 1, 2017, the time-charter swap counter-party did not exercise the two -month option and as such, the agreement was completed as of June 30, 2017. Forward freight agreements The Company uses forward freight agreements (or FFAs ) in non-hedge-related transactions to increase or decrease its exposure to spot market rates, within defined limits. Net gains and losses from FFAs are recorded within realized and unrealized gain (loss) on derivative instruments in the Company's consolidated statements of loss. The following table presents the location and fair value amounts of derivative instruments, segregated by type of contract, on the Company’s consolidated balance sheets. Current portion of derivative assets Derivative assets Accounts receivables (Accrued liabilities) $ $ $ As at September 30, 2018 Interest rate swap agreements 2,973 5,531 394 Forward freight agreements 102 — (4 ) 3,075 5,531 390 As at December 31, 2017 Interest rate swap agreements 1,016 4,226 (39 ) 1,016 4,226 (39 ) Realized and unrealized gains (losses) relating to the interest rate swaps, stock purchase warrant, time-charter swap and forward freight agreements are recognized in earnings and reported in realized and unrealized gain (loss) on derivative instruments in the Company’s consolidated statements of loss as follows: Three Months Ended Three Months Ended September 30, 2018 September 30, 2017 Realized gains (losses) Unrealized gains (losses) Total Realized (losses) gains Unrealized gains (losses) Total $ $ $ $ $ $ Interest rate swap agreements 711 13 724 (154 ) 401 247 Forward freight agreements (119 ) (9 ) (128 ) 234 (91 ) 143 592 4 596 80 310 390 Nine Months Ended Nine Months Ended September 30, 2018 September 30, 2017 Realized gains (losses) Unrealized gains Total Realized (losses) gains Unrealized gains (losses) Total $ $ $ $ $ $ Interest rate swap agreements 1,575 3,262 4,837 (894 ) 2 (892 ) Stock purchase warrant — — — — (287 ) (287 ) Time-charter swap agreement — — — 1,106 (875 ) 231 Forward freight agreements (137 ) 25 (112 ) 347 (108 ) 239 1,438 3,287 4,725 559 (1,268 ) (709 )

Other Expense

Other Expense	9 Months Ended
	Sep. 30, 2018
Other Liabilities Disclosure [Abstract]
Other Expense	Other Expense The components of other expense are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 $ $ $ $ Freight tax provision (2,050 ) (1,864 ) (10,014 ) (6,296 ) Foreign exchange gain 1,251 81 6,025 151 Other income — 15 49 227 Total (799 ) (1,768 ) (3,940 ) (5,918 ) The following reflects the changes in the Company’s potential tax on freight income, recorded in other long-term liabilities, from January 1, 2018 to September 30, 2018 : 2018 $ Balance of unrecognized tax benefits as at January 1 26,054 Increases for positions related to the current period 2,099 Changes for positions taken in prior periods 1,852 Decreases related to statute of limitations (93 ) Balance of unrecognized tax benefits as at September 30 29,912 The Company does not presently anticipate its uncertain tax positions will significantly increase or decrease in the next 12 months; however, actual developments could differ from those currently expected.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Financial Instruments	Financial Instruments a. Fair Value Measurements For a description of how the Company estimates fair value and for a description of the fair value hierarchy levels, see note 12 to the Company’s audited consolidated financial statements filed with its Annual Report on Form 20-F for the year ended December 31, 2017 . The following table includes the estimated fair value and carrying value of those assets and liabilities that are measured at fair value on a recurring and non-recurring basis as well as the estimated fair value of the Company’s financial instruments that are not accounted for at the fair value on a recurring basis. September 30, 2018 December 31, 2017 Fair Value Hierarchy Level Carrying Amount Asset / (Liability) $ Fair Value Asset / (Liability) $ Carrying Amount Asset / (Liability) $ Fair Value Asset / (Liability) $ Recurring: Cash and cash equivalents and restricted cash Level 1 58,827 58,827 75,710 75,710 Derivative instruments (note 9) Interest rate swap agreements (1) Level 2 8,504 8,504 5,242 5,242 Forward freight agreements (1) Level 2 102 102 — — Other: Advances to equity accounted investments Note (2) 9,930 Note (2) 9,930 Note (2) Long-term debt, including current portion Level 2 (807,078 ) (793,851 ) (952,302 ) (946,105 ) Obligations related to capital leases, including current portion Level 2 (296,710 ) (290,849 ) (148,908 ) (147,401 ) (1) The fair value of the Company’s interest rate swap agreements and FFAs at September 30, 2018 and December 31, 2017 excludes accrued interest income and expenses which are recorded in accounts receivables and accrued liabilities, respectively, on the unaudited consolidated balance sheets. (2) The advances to equity-accounted investments together with the Company’s investments in the equity-accounted investments form the net aggregate carrying value of the Company’s interests in the equity-accounted investments in these consolidated financial statements. The fair values of the individual components of such aggregate interests as at September 30, 2018 and December 31, 2017 were not determinable. b. Financing Receivables The following table contains a summary of the Company’s financing receivables by type and the method by which the Company monitors the credit quality of its financing receivables on a quarterly basis. September 30, 2018 December 31, 2017 Class of Financing Receivable Credit Quality Indicator Grade $ $ Advances to equity accounted investments Other internal metrics Performing 9,930 9,930 Total 9,930 9,930

Capital Stock and Stock-Based C

Capital Stock and Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Capital Stock and Stock-Based Compensation	Capital Stock and Stock-Based Compensation The authorized capital stock of the Company at September 30, 2018 was 100,000,000 shares of preferred stock (December 31, 2017 - 100,000,000 ), with a par value of $0.01 per share, 485,000,000 shares of Class A common stock (December 31, 2017 - 285,000,000 ), with a par value of $0.01 per share, and 100,000,000 shares of Class B common stock (December 31, 2017 - 100,000,000 ), with a par value of $0.01 per share. A share of Class A common stock entitles the holder to one vote per share while a share of Class B common stock entitles the holder to five votes per share, subject to a 49% aggregate Class B common stock voting power maximum. As of September 30, 2018 , the Company had 231.6 million shares of Class A common stock ( December 31, 2017 – 231.2 million ), 37.0 million shares of Class B common stock ( December 31, 2017 – 37.0 million ) and no shares of preferred stock ( December 31, 2017 – nil ) issued and outstanding. During March 2018, a total of 168,029 shares of Class A common stock with an aggregate value of $0.2 million and 0.5 million stock options with an exercise price of $1.22 per share were granted to the Company’s non-management directors as part of their annual compensation for 2017. These stock options have a ten -year term and vest immediately. These shares of Class A common stock and stock options were issued under the Teekay Tankers Ltd. 2007 Long-Term Incentive Plan and distributed to the directors. During March 2017, 0.4 million stock options with an exercise price of $2.23 per share were granted to non-management directors of the Company. For the nine months ended September 30, 2018 and September 30, 2017 , the compensation relating to the granting of such stock and stock options has been included in general administrative expenses in the amount of $0.4 million and $0.3 million , respectively. The Company also grants stock options and restricted stock units as incentive-based compensation under the Teekay Tankers Ltd. 2007 Long-Term Incentive Plan to the officers of the Company and certain employees of Teekay subsidiaries that provide services to the Company. The Company measures the cost of such awards using the grant date fair value of the award and recognizes that cost, net of estimated forfeitures, over the requisite service period. The requisite service period consists of the period from the grant date of the award to the earlier of the date of vesting or the date the recipient becomes eligible for retirement. For stock-based compensation awards subject to graded vesting, the Company calculates the value for the award as if it was one single award with one expected life and amortizes the calculated expense for the entire award on a straight-line basis over the requisite service period. The compensation cost of the Company's stock-based compensation awards is reflected in general and administrative expenses in the Company’s consolidated statements of loss. During March 2018, the Company granted 0.7 million stock options with an exercise price of $1.22 per share to the officers of the Company and certain employees of Teekay subsidiaries that provide services to the Company. During March 2017, the Company granted 0.5 million stock options with an exercise price of $2.23 per share to an officer of the Company. Each stock option has a ten -year term and vests equally over three years from the grant date. The weighted-average fair value of the stock options granted in 2018 to non-management directors and to officers was $0.35 (2017 - $0.67 ) per option, estimated on the grant date using the Black-Scholes option pricing model. The following assumptions were used in computing the fair value of the stock options granted: expected volatility of 48.7% (2017 - 50.2% ); expected life of five years (2017 - five years); dividend yield of 5.5% (2017 - 5.0% ); and risk-free interest rate of 2.6% (2017 - 2.1% ). The expected life of the stock options granted was estimated using the historical exercise behavior of employees of Teekay that receive stock options from Teekay. The expected volatility was based on historical volatility as calculated using historical data during the five years prior to the grant date. During March 2018, the Company also granted 0.8 million (2017 - 0.4 million ) restricted stock units to the officers of the Company and certain employees of Teekay subsidiaries that provide services to the Company with an aggregate fair value of $0.9 million (2017 - $0.8 million ). Each restricted stock unit is equal to one share of the Company’s common stock plus reinvested distributions from the grant date to the vesting date. The restricted stock units vest equally over three years from the grant date. Any portion of a restricted stock unit award that is not vested on the date of the recipient’s termination of service is cancelled, unless their termination arises as a result of the recipient’s retirement and, in this case, the restricted stock unit award will continue to vest in accordance with the vesting schedule. Upon vesting, the value of the restricted stock unit awards, net of withholding taxes, is paid to each recipient in the form of common stock. During the three and nine months ended September 30, 2018 , the Company recorded $0.2 million and $0.8 million (September 30, 2017 - $0.2 million and $0.8 million ), respectively, of expenses related to the restricted stock units and stock options. During the nine months ended September 30, 2018 , a total of 0.3 million restricted stock units (2017 - 0.3 million ) with a market value of $0.3 million (2017 - $0.6 million ) vested and was paid to the grantees by issuing 0.2 million shares (2017 - 0.2 million shares) of Class A common stock, net of withholding taxes.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Management Fee - Related and Other a. Teekay, and its wholly-owned subsidiary and the Company's manager, Teekay Tankers Management Services Ltd. (or the Manager ), provide commercial, technical, strategic and administrative services to the Company pursuant to a long-term management agreement (the Management Agreement ). In addition, the Manager has subcontracted with TTOL and its affiliates to provide certain commercial and technical services to the Company, except for certain vessels acquired in the merger with TIL, which are technically managed by a third party. Certain of the Company’s vessels participate in RSAs managed by TTOL. Amounts received and paid by the Company for such related party transactions for the periods indicated were as follows: Three Months Ended Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 $ $ $ $ RSA pool management fees and commissions (i) — — — (2,799 ) Commercial management fees (ii) — — — (1,187 ) Vessel operating expenses - technical management fee (iii) (2,800 ) (2,020 ) (8,900 ) (6,442 ) Strategic and administrative service fees (iv) (7,875 ) (6,761 ) (25,204 ) (13,678 ) Secondment fees (v) (189 ) (148 ) (548 ) (188 ) LNG service revenues (vi) 72 84 344 252 Technical management fee revenue (vii) 3,490 3,828 9,819 5,048 Service revenues (viii) 343 1,003 758 1,280 Entities under Common Control (note 4) RSA pool management fees and commissions (i) — — — 2,799 Commercial management fees (ii) — — — 1,187 Strategic and administrative service fees (iv) — — — (7,026 ) Technical management fee revenue (vii) — — — 4,890 Service revenues (viii) — — — 1,772 (i) Prior to 2018, the Company’s share of TTOL’s fees for RSAs are reflected as a reduction to net pool revenues on the Company’s consolidated statements of loss. The Company acquired the remaining 50% interest in TTOL on May 31, 2017 (notes 4 and 6 (c)). Subsequent to the acquisition, the Company's share of TTOL's fees has been eliminated. (ii) The Manager’s commercial management fees for vessels on time-charter out contracts and spot-traded vessels that are not included in the RSAs are reflected in voyage expenses on the Company’s consolidated statements of loss. Subsequent to the Company's acquisition of the remaining 50% interest in TTOL, the Company's share of the Manager's commercial management fees has been eliminated. (iii) The cost of ship management services provided by the Manager has been presented as vessel operating expenses on the Company's consolidated statements of loss. (iv) The Manager's strategic and administrative service fees have been presented in general and administrative expenses on the Company's consolidated statements of loss. The Company's executive officers are employees of Teekay or subsidiaries thereof, and their compensation (other than any awards under the Company's long-term incentive plan described in note 12 ) is set and paid by Teekay or such other subsidiaries. The Company reimburses Teekay for time spent by its executive officers on the Company's management matters through the strategic portion of the management fee. (v) The Company pays secondment fees for services provided by some employees of Teekay. Secondment fees have been presented in general and administrative expenses on the Company's consolidated statements of loss. (vi) The Company's ship-to-ship transfer business has an operational and maintenance subcontract with Teekay LNG Bahrain Operations L.L.C., an entity wholly-owned by TGP (which is controlled by Teekay), for the Bahrain LNG Import Terminal (or the Terminal ). The Terminal is owned by Bahrain LNG W.I.L., a joint venture for which Teekay LNG Operating L.L.C., an entity wholly-owned by TGP, has a 30% interest. The Company's ship-to-ship transfer business also has a services agreement with Teekay Shipping Ltd., an entity wholly-owned by Teekay, to provide certain LNG services. (vii) The Company receives reimbursements from Teekay who subcontracts technical management services from the Manager. These reimbursements have been presented in general and administrative expenses on the Company's consolidated statements of loss. (viii) The Company recorded revenue relating to TTOL's administration of certain RSAs and provision of certain commercial services to participants in the arrangements. The Company also recorded revenues of $1.8 million for the nine months ended September 30, 2017 associated with the Entities under Common Control. b. The Manager and other subsidiaries of Teekay collect revenues and remit payments for expenses incurred by the Company’s vessels. Such amounts, which are presented on the Company’s consolidated balance sheets in "due from affiliates" or "due to affiliates," as applicable, are without interest or stated terms of repayment. The amounts owing from the RSAs for monthly distributions are reflected in the consolidated balance sheets as pool receivable from affiliates, are without interest and are repayable upon the terms contained within the applicable pool agreement. The Company had advanced $48.3 million and $45.1 million as at September 30, 2018 and December 31, 2017 , respectively, to the RSAs for working capital purposes. These amounts, which are reflected in the consolidated balance sheets in due from affiliates, are without interest and are repayable when applicable vessels leave the RSAs. c. Pursuant to a service agreement with the Teekay Aframax RSA, from time to time, the Company may hire vessels to perform full service lightering services. In the three and nine months ended September 30, 2018 , the Company recognized $3.3 million and $19.1 million ( September 30, 2017 - $2.9 million and $10.3 million ), respectively, related to vessels which were chartered-in from the RSA to assist with full service lightering operations. These amounts have been presented in voyage expenses on the Company's consolidated statements of loss.

Sales of Vessels

Sales of Vessels	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Sales of Vessels	Sales of Vessels The Company's consolidated statements of loss for the nine months ended September 30, 2018 include a net gain on sale of vessels of $0.2 million relating to one lightering support vessel which was sold and delivered to its buyer in the second quarter of 2018. In September 2018, the Company completed a $156.6 million sale-leaseback financing transaction relating to six of the Company's Aframax tankers (see note 8). In November 2018, the Company completed a $84.7 million sale-leaseback financing transaction relating to four of the Company's vessels including two Aframax tankers, one Suezmax tanker and one LR2 product tanker (see note 20). The Company’s consolidated statements of loss for the three and nine months ended September 30, 2017 include a net loss on sale of vessels of $7.9 million and $12.5 million , respectively, relating to three Aframax tankers and one lightering support vessel, which were sold and delivered to their respective buyers in the second, third and fourth quarters of 2017, and two Suezmax tankers, which were sold in the first quarter of 2017. In July 2017, the Company completed a $153.0 million sale-leaseback financing transaction relating to four of the Company's Suezmax tankers (see note 8).

Loss Per Share

Loss Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Loss Per Share	Loss Per Share The net loss available for common shareholders and loss per common share presented in the table below includes the results of operations of the Entities under Common Control which were not purchased solely with cash (note 4): Three Months Ended Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 $ $ $ $ Net loss (17,484 ) (22,380 ) (64,050 ) (56,144 ) Weighted average number of common shares – basic (1) 268,558,556 179,224,094 268,470,804 178,853,698 Dilutive effect of stock-based awards — — — — Weighted average number of common shares – diluted (1) 268,558,556 179,224,094 268,470,804 178,853,698 Loss per common share: – Basic (0.07 ) (0.12 ) (0.24 ) (0.31 ) – Diluted (0.07 ) (0.12 ) (0.24 ) (0.31 ) (1) The weighted-average number of common shares outstanding for periods prior to May 2017 has been retroactively adjusted to include approximately 13.8 million shares of the Company's Class B common stock issued to Teekay as consideration for the acquisition of 50% of TTOL in May 2017. Stock-based awards that have an anti-dilutive effect on the calculation of diluted earnings per common share, are excluded from this calculation. In the periods where a loss attributable to shareholders has been incurred, all stock-based awards are anti-dilutive. For the three and nine months ended September 30, 2018, 0.3 million and 0.3 million restricted stock units ( September 30, 2017 - 0.6 million and 0.3 million ), respectively, had an anti-dilutive effect on the calculation of diluted earnings per common share. For the three and nine months ended September 30, 2018, options to acquire 2.9 million and 2.9 million ( September 30, 2017 - 1.7 million and 1.6 million ) shares, respectively, of the Company’s Class A common stock had an anti-dilutive effect on the calculation of diluted earnings per common share.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Total cash, cash equivalents and restricted cash is as follows: As at As at As at As at September 30, 2018 December 31, 2017 September 30, 2017 December 31, 2016 $ $ $ $ Cash and cash equivalents 54,361 71,439 60,606 94,157 Restricted cash – current 1,794 1,599 1,645 750 Restricted cash – long-term 2,672 2,672 2,672 — 58,827 75,710 64,923 94,907 The Company maintains restricted cash deposits relating to certain forward freight agreements (note 9), LNG terminal management and leasing arrangements (see note 8).

Liquidity

Liquidity	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Liquidity	Liquidity Management is required to assess if the Company will have sufficient liquidity to continue as a going concern for the one-year period following the issuance of its financial statements. The Company has a loan facility, with an outstanding balance of $47.6 million , that matured in the fourth quarter of 2018. During the fourth quarter of 2018, the Company completed an additional sale-leaseback financing transaction for four vessels (see note 20), some of the net proceeds of which were used to refinance the loan facility, which was scheduled to mature in November 2018, and to prepay a portion of the Company's 2016 Debt Facility. The Company also completed a loan to finance working capital for the Company's RSA commercial management pool operations (see note 20). Based on the Company’s liquidity at the date these consolidated financial statements were issued, including the fourth quarter financing transactions described above and the liquidity it expects to generate from operations over the following year based on an expected tanker market recovery, the Company estimates that it will have sufficient liquidity to continue as a going concern for at least the one-year period following the issuance of these consolidated financial statements.

Acquisition of Tanker Investmen

Acquisition of Tanker Investments Ltd. Acquisition of Tanker Investments Ltd.	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisition of Tanker Investments Ltd.	Acquisition of Tanker Investments Ltd. On May 31, 2017, the Company entered into a merger agreement to acquire the remaining 27.0 million issued and outstanding common shares of TIL, by way of a share-for-share exchange of 3.3 shares of Class A common stock of the Company for each outstanding share of TIL common stock not owned by the Company. On November 17, 2017, the Company's shareholders voted in favor of increasing the authorized number of its Class A common shares to permit the issuance of Class A common shares as consideration for the merger with TIL. Concurrently, the merger was approved by the shareholders of TIL. The Company amended its amended and restated articles of incorporation and completed the merger on November 27, 2017, as a result of which, TIL became a wholly-owned subsidiary of the Company. As consideration for the merger, the Company issued 88,977,544 Class A common shares to the TIL shareholders (other than the Company and its subsidiaries) for $151.3 million , or $1.70 per share. Pursuant to this acquisition, the Company acquired a modern fleet of 10 Suezmax tankers, six Aframax tankers and two LR2 product tankers with an average age of 7.3 years, assumed $47.1 million of net working capital and long-term liabilities and assumed long-term debt with a principal balance outstanding of $338.9 million . The merger with TIL was accounted for as an acquisition of assets. The purchase price of the acquisition consisted of the fair value of the Company's shares issued on the merger date ( $151.3 million ), the transaction costs associated with the merger ( $6.9 million ) and the fair value of the Company's 11.3% pre-existing ownership in TIL at the close of the merger ( $19.2 million ), for a total acquisition cost of $177.4 million . Net working capital and long-term liabilities of $47.1 million and $337.1 million of long-term debt assumed were recognized at their fair values on November 27, 2017. The remaining amount of the purchase price was allocated to vessels ( $467.2 million ) and existing time-charter contracts ( $0.2 million ), on a relative fair value basis.

Shipbuilding Contracts

Shipbuilding Contracts	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Shipbuilding Contracts	Shipbuilding Contracts In April 2013, four special purpose subsidiary companies of the Company entered into agreements with STX Offshore & Shipbuilding Co., Ltd (or STX ) of South Korea to construct four , fuel-efficient 113,000 dead-weight tonne Long Range 2 (or LR2 ) product tanker newbuildings. At the same time, the Company entered an Option Agreement with STX allowing the Company to order up to an additional 12 vessels. In February and March 2014, the Company and its subsidiaries commenced legal proceedings against STX for having repudiated the four firm shipbuilding contracts and the Option Agreement in London, U.K. In the same year, STX have issued proceedings in Korea. On February 15, 2016, each of the Company’s four subsidiaries had successfully obtained an English Court Order requiring STX to pay a total of $8.9 million , per subsidiary, in respect of the four firm shipbuilding contracts. STX filed for bankruptcy protection and as of December 31, 2016, all Korean enforcement actions were stayed. STX has had that protection recognized in England and Wales. The Company was not in a position to take any further action on enforcement and recognition of its award in the U.K. or Korea while the bankruptcy protection remained in place. In March 2017, the Korean courts upheld the Company's subsidiaries' claims for the firm contracts in the bankruptcy proceedings. In November 2017, STX underwent a rehabilitation plan which resulted in the Company's subsidiaries being entitled to receive 7% of the award in cash to be paid over the next eight years until 2026, and 93% of the award in equity of STX. In June 2018, the Company's subsidiaries, under their entitlement as part of the STX rehabilitation plan, received a total of 315,856 shares of STX, representing a minor percentage ownership interest. As at September 30, 2018, the STX shares had been de-listed. No amounts have been recorded due to uncertainty of their value. In addition, the Company has not recognized a receivable in respect to the non-interest-bearing cash award due to uncertainty of collection.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events a. In November 2018, the Company completed an $84.7 million sale-leaseback financing transaction relating to four of the Company's vessels including two Aframax tankers, one Suezmax tanker and one LR2 product tanker. Each vessel is leased on a bareboat charter with terms ranging from 10 to 12 years, with fixed daily rates on the charters ranging between $5,000 and $7,800 , and with purchase options for all four vessels throughout the remaining lease term beginning in October 2021. The Company also has options to purchase each vessel upon maturity of the bareboat charters . Proceeds from the sale-leaseback transaction were used to refinance one of the Company's corporate revolvers, which had an outstanding balance of $47.6 million as at September 30, 2018 and was scheduled to mature in November 2018, and to prepay a portion of the Company's 2016 Debt Facility. b. In November 2018, the Company entered into a working capital loan facility agreement which provides available aggregate borrowings of up to $40.0 million and is expected to increase the Company's liquidity by approximately $20.0 million .

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Accounting	The unaudited interim consolidated financial statements (or consolidated financial statements ) have been prepared in conformity with United States generally accepted accounting principles (or GAAP ). These consolidated financial statements include the accounts of Teekay Tankers Ltd., its wholly-owned subsidiaries, equity-accounted investments, the Entities under Common Control (as defined in note 4 ) and any variable interest entities (or VIEs ) of which it is the primary beneficiary (collectively, the Company ). The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Certain information and footnote disclosures required by GAAP for complete annual financial statements have been omitted and, therefore, these consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements for the year ended December 31, 2017 , filed on Form 20-F with the U.S. Securities and Exchange Commission (or the SEC ) on April 24, 2018. In the opinion of management, these consolidated financial statements reflect all adjustments, consisting solely of a normal recurring nature, necessary to present fairly, in all material respects, the Company’s consolidated financial position, results of operations, and cash flows for the interim periods presented. The results of operations for the interim periods presented are not necessarily indicative of those for a full fiscal year. Significant intercompany balances and transactions have been eliminated upon consolidation.
Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board (or FASB ) issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers , (or ASU 2014-09 ). ASU 2014-09 requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This update creates a five-step model that requires entities to exercise judgment when considering the terms of the contract(s) which include (i) identifying the contract(s) with the customer, (ii) identifying the separate performance obligations in the contract, (iii) determining the transaction price, (iv) allocating the transaction price to the separate performance obligations, and (v) recognizing revenue as each performance obligation is satisfied. ASU 2014-09 became effective for the Company as of January 1, 2018 and may be applied, at the Company’s option, retrospectively to each period presented or as a cumulative-effect adjustment as of such date. The Company has elected to apply ASU 2014-09 only to those contracts that were not completed as of January 1, 2018. The Company has adopted ASU 2014-09 as a cumulative-effect adjustment as of the date of adoption. The Company has identified the following differences on adoption of ASU 2014-09: • The Company previously presented the net allocation for its vessels participating in revenue sharing arrangements (or RSAs ) as net pool revenues. The Company has determined that it is the principal in voyages its vessels perform that are included in the RSAs. As such, the revenue from those voyages is presented in voyage charter revenues and the difference between this amount and the Company's net allocation from the RSA is presented as voyage expenses. This had the effect of increasing voyage charter revenues and voyage expenses for the three and nine months ended September 30, 2018 by $73.6 million and $202.4 million , respectively. There was no cumulative impact to opening equity as at January 1, 2018. • The Company previously presented all accrued revenue as a component of accounts receivable. The Company has determined that if the right to such consideration is conditioned upon something other than the passage of time, such accrued revenue should be presented apart from accounts receivable. This had the effect of increasing other current assets and decreasing accounts receivable by $1.4 million at September 30, 2018 . In February 2016, FASB issued Accounting Standards Update 2016-02, Leases (or ASU 2016-02 ). ASU 2016-02 establishes a right-of-use model that requires a lessee to record a right-of-use asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. For lessees, leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. ASU 2016-02 requires lessors to classify leases as a sales-type, direct financing, or operating lease. A lease is a sales-type lease if any one of five criteria are met, each of which indicate that the lease, in effect, transfers control of the underlying asset to the lessee. If none of those five criteria are met, but two additional criteria are both met, indicating that the lessor has transferred substantially all of the risks and benefits of the underlying asset to the lessee and a third party, the lease is a direct financing lease. All leases that are not sales-type leases or direct financing leases are operating leases. ASU 2016-02 is effective January 1, 2019, with early adoption permitted. FASB issued an additional accounting standards update in July 2018 that made further amendments to accounting for leases, including allowing the use of a transition approach whereby a cumulative effect adjustment is made as of the effective date, with no retrospective effect. The Company has elected to use this new optional transition approach. The Company will adopt ASU 2016-02 on January 1, 2019. To determine the cumulative effect adjustment, the Company will not reassess lease classification, initial direct costs for any existing leases and whether any expired or existing contracts are or contain leases. The adoption of ASU 2016-02 will result in a change in a ccounting method for the lease portion of the daily charter hire for the Company’s chartered-in vessels accounted for as operating leases with firm periods of greater than one year. Under ASU 2016-02, the Company will recognize a right-of-use asset and a lease liability on the balance sheet for these charters based on the present value of future minimum lease payments, whereas currently no right-of-use asset or lease liability is recognized. This will have the result of increasing the Company’s assets and liabilities. The pattern of expense recognition of chartered-in vessels is expected to remain substantially unchanged, unless the right-of-use asset becomes impaired. The Company is expecting to disclose in its consolidated financial statements for the year ended December 31, 2018 the quantitative impact of adopting ASU 2016-02. In June 2016, the FASB issued Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments . This update replaces the incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. This update is effective for the Company as of January 1, 2020, with a modified-retrospective approach. The Company is currently evaluating the effect of adopting this new guidance. In August 2016, the FASB issued Accounting Standards Update 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments , which, among other things, provides guidance on two acceptable approaches of classifying distributions received from equity method investees in the statement of cash flows. This update became effective for the Company as of January 1, 2018, with a retrospective approach. The Company has elected to classify distributions received from equity method investees in the statement of cash flows based on the nature of the distribution. The adoption of this update did not have a material impact on the Company. In November 2016, the FASB issued Accounting Standards Update 2016-18, Statement of Cash Flows: Restricted Cash , (or ASU 2016-18 ). ASU 2016-18 requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Entities are also required to reconcile such total to amounts on the balance sheet and disclose the nature of the restrictions. ASU 2016-18 became effective for the Company as of January 1, 2018. Adoption of ASU 2016-18 resulted in the Company including in its statement of cash flows changes in cash, cash equivalents and restricted cash.

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table contains a breakdown of the Company's revenue by contract type for the three and nine months ended September 30, 2018 and September 30, 2017 . All revenue is part of the Company's conventional tanker segment, except for revenue for ship-to-ship support services and LNG terminal management, consultancy, procurement and other related services, which is part of the Company's ship-to-ship transfer segment. Three Months Ended Three Months Ended Nine Months Ended Nine Months Ended Voyage charters (1) Suezmax 90,267 271 243,771 12,905 Aframax 29,210 4,869 76,952 13,900 LR2 16,712 — 40,312 — Full service lightering 15,858 20,257 70,982 68,076 Total 152,047 25,397 432,017 94,881 Time-charters Aframax 7,784 12,318 31,608 36,975 Suezmax 2,909 9,167 13,063 35,918 LR2 1,633 3,196 7,149 12,209 Total 12,326 24,681 51,820 85,102 Other revenue Ship-to-ship support services 8,217 7,980 22,452 28,210 Commercial management 2,050 3,112 6,246 9,448 LNG terminal management, consultancy and other 1,275 1,822 3,504 4,336 Total 11,542 12,914 32,202 41,994 Net pool revenues (1) Suezmax — 18,820 — 66,261 Aframax — 4,832 — 23,195 LR2 — 4,598 — 19,067 MR — (4 ) — 12 Total — 28,246 — 108,535 Total revenues 175,915 91,238 516,039 330,512 (1) Prior to the January 1, 2018 adoption of ASU 2014-09, the Company presented the net allocation for its vessels participating in RSAs as net pool revenues. The Company has determined that it is the principal in voyages its vessels perform that are included in the RSAs. As such, the revenue from those voyages is presented in voyage charter revenues and the difference between this amount and the Company's net allocation from the RSA is presented as voyage expenses. The adoption of ASU 2014-09 had the impact of increasing voyage charter revenues and voyage expenses for the three and nine months ended September 30, 2018 by $73.6 million and $202.4 million , respectively.

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Company's Revenue and Income from Operations by Segment	The following tables include results for the Company’s revenues and (loss) income from operations by segment for the three and nine months ended September 30, 2018 and September 30, 2017 . Three Months Ended September 30, 2018 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 166,423 12,019 (2,527 ) 175,915 Voyage expenses (3) (85,575 ) — 2,527 (83,048 ) Vessel operating expenses (43,432 ) (8,729 ) — (52,161 ) Time-charter hire expense (2,935 ) (1,382 ) — (4,317 ) Depreciation and amortization (28,532 ) (1,063 ) — (29,595 ) General and administrative expenses (4) (7,985 ) (762 ) — (8,747 ) Restructuring charges — (213 ) — (213 ) Loss from operations (2,036 ) (130 ) — (2,166 ) Equity loss (359 ) — — (359 ) Three Months Ended September 30, 2017 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 81,758 11,902 (2,422 ) 91,238 Voyage expenses (3) (20,725 ) — 2,422 (18,303 ) Vessel operating expenses (32,227 ) (8,731 ) — (40,958 ) Time-charter hire expense (4,629 ) (1,206 ) — (5,835 ) Depreciation and amortization (23,071 ) (1,257 ) — (24,328 ) General and administrative expenses (4) (6,823 ) (799 ) — (7,622 ) (Loss) gain on sale of vessels (7,968 ) 42 — (7,926 ) Loss from operations (13,685 ) (49 ) — (13,734 ) Equity loss (274 ) — — (274 ) Nine Months Ended September 30, 2018 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 490,083 35,061 (9,105 ) 516,039 Voyage expenses (3) (259,079 ) — 9,105 (249,974 ) Vessel operating expenses (131,886 ) (25,922 ) — (157,808 ) Time-charter hire expense (10,326 ) (4,371 ) — (14,697 ) Depreciation and amortization (85,171 ) (3,427 ) — (88,598 ) General and administrative expenses (4) (25,385 ) (2,554 ) — (27,939 ) Gain on sale of vessels — 170 — 170 Restructuring charges (152 ) (1,043 ) — (1,195 ) Loss from operations (21,916 ) (2,086 ) — (24,002 ) Equity income 265 — — 265 Nine months ended September 30, 2017 Conventional Tanker Segment Ship-to-Ship Transfer Segment (2) Inter-segment Adjustment (1) Total $ $ $ $ Revenues (3) 299,154 39,387 (8,029 ) 330,512 Voyage expenses (3) (69,517 ) — 8,029 (61,488 ) Vessel operating expenses (100,586 ) (31,363 ) — (131,949 ) Time-charter hire expense (23,698 ) (3,761 ) — (27,459 ) Depreciation and amortization (69,857 ) (3,795 ) — (73,652 ) General and administrative expenses (4) (22,258 ) (2,617 ) — (24,875 ) (Loss) gain on sale of vessels (12,545 ) 50 — (12,495 ) Income (loss) from operations 693 (2,099 ) — (1,406 ) Equity loss (27,174 ) — — (27,174 ) (1) The ship-to-ship transfer segment provides lightering support services to the conventional tanker segment for full service lightering operations and the pricing for such services was based on actual costs incurred. (2) Revenues, net of the inter-segment adjustment, earned from the ship-to-ship transfer segment are reflected in Other Revenues in the Company's consolidated statements of loss. (3) The comparative periods do not include the impact of the January 1, 2018 adoption of ASU 2014-09 (see note 2). (4) Includes direct general and administrative expenses and indirect general and administrative expenses (allocated to each segment based on estimated use of corporate resources).
Reconciliation of Total Segment Assets to Total Assets Presented in Consolidated Balance Sheets	A reconciliation of total segment assets to total assets presented in the accompanying consolidated balance sheets is as follows: As at As at September 30, 2018 December 31, 2017 $ $ Conventional Tanker Segment 2,036,698 2,089,099 Ship-to-Ship Transfer Segment 38,135 36,810 Cash and cash equivalents 54,361 71,439 Consolidated total assets 2,129,194 2,197,348

Investments in and Advances t_2

Investments in and Advances to Equity Accounted Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Investments in and Advances to Equity Accounted Investments	As at September 30, 2018 As at December 31, 2017 $ $ High-Q Joint Venture 24,811 24,546 Gemini Tankers L.L.C. — 914 Total 24,811 25,460

Long-Term Debt (Tables)

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Summary of Long-Term Debt	As at As at September 30, 2018 December 31, 2017 $ $ Revolving Credit Facilities due through 2022 465,763 539,735 Term Loans due through 2021 348,946 423,512 Total principal 814,709 963,247 Less: unamortized discount and debt issuance costs (7,631 ) (10,945 ) Total debt 807,078 952,302 Less: current portion (103,843 ) (166,745 ) Non-current portion of long-term debt 703,235 785,557

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2018
Leases [Abstract]
Capital Lease Obligations	As at As at September 30, 2018 December 31, 2017 $ $ Aframax tankers 153,140 — Suezmax tankers 143,570 148,908 Total obligations related to capital leases 296,710 148,908 Less: current portion (15,839 ) (7,227 ) Long-term obligations related to capital leases 280,871 141,681
Schedule of Future Minimum Lease Payments for Capital Leases	As at September 30, 2018 , the Company's remaining commitments under the 10 capital leases for the Suezmax and Aframax tankers was approximately $445.3 million , including imputed interest of $148.6 million , repayable from 2018 through 2029, as indicated below, excluding the sale-leaseback transaction described in note 20: Year Commitment Remaining 2018 $ 9,574 2019 $ 37,954 2020 $ 38,052 2021 $ 37,943 2022 $ 37,936 Thereafter $ 283,836

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Interest Rate Swap Positions	As at September 30, 2018 , the Company was committed to the following interest rate swap agreements: Interest Rate Notional Amount Fair Value / Carrying Amount of Asset Remaining Term Fixed Interest Rate Index $ $ (years) (%) (1) LIBOR-Based Debt: U.S. Dollar-denominated interest rate swaps (2) LIBOR 104,133 1,770 2.3 1.46 U.S. Dollar-denominated interest rate swaps LIBOR 150,000 4,720 2.3 1.55 U.S. Dollar-denominated interest rate swaps LIBOR 50,000 2,014 2.3 1.16 (1) Excludes the margin the Company pays on its variable-rate debt, which, as of September 30, 2018 , ranged from 0.30% to 2.75% . (2) Notional amount reduces quarterly.
Schedule of Derivative Instruments	The following table presents the location and fair value amounts of derivative instruments, segregated by type of contract, on the Company’s consolidated balance sheets. Current portion of derivative assets Derivative assets Accounts receivables (Accrued liabilities) $ $ $ As at September 30, 2018 Interest rate swap agreements 2,973 5,531 394 Forward freight agreements 102 — (4 ) 3,075 5,531 390 As at December 31, 2017 Interest rate swap agreements 1,016 4,226 (39 ) 1,016 4,226 (39 )
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location	Realized and unrealized gains (losses) relating to the interest rate swaps, stock purchase warrant, time-charter swap and forward freight agreements are recognized in earnings and reported in realized and unrealized gain (loss) on derivative instruments in the Company’s consolidated statements of loss as follows: Three Months Ended Three Months Ended September 30, 2018 September 30, 2017 Realized gains (losses) Unrealized gains (losses) Total Realized (losses) gains Unrealized gains (losses) Total $ $ $ $ $ $ Interest rate swap agreements 711 13 724 (154 ) 401 247 Forward freight agreements (119 ) (9 ) (128 ) 234 (91 ) 143 592 4 596 80 310 390 Nine Months Ended Nine Months Ended September 30, 2018 September 30, 2017 Realized gains (losses) Unrealized gains Total Realized (losses) gains Unrealized gains (losses) Total $ $ $ $ $ $ Interest rate swap agreements 1,575 3,262 4,837 (894 ) 2 (892 ) Stock purchase warrant — — — — (287 ) (287 ) Time-charter swap agreement — — — 1,106 (875 ) 231 Forward freight agreements (137 ) 25 (112 ) 347 (108 ) 239 1,438 3,287 4,725 559 (1,268 ) (709 )

Other Expense (Tables)

Other Expense (Tables)	9 Months Ended
	Sep. 30, 2018
Other Liabilities Disclosure [Abstract]
Components of Other Expense	The components of other expense are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 $ $ $ $ Freight tax provision (2,050 ) (1,864 ) (10,014 ) (6,296 ) Foreign exchange gain 1,251 81 6,025 151 Other income — 15 49 227 Total (799 ) (1,768 ) (3,940 ) (5,918 )
Unrecognized Tax Benefits Roll Forward	The following reflects the changes in the Company’s potential tax on freight income, recorded in other long-term liabilities, from January 1, 2018 to September 30, 2018 : 2018 $ Balance of unrecognized tax benefits as at January 1 26,054 Increases for positions related to the current period 2,099 Changes for positions taken in prior periods 1,852 Decreases related to statute of limitations (93 ) Balance of unrecognized tax benefits as at September 30 29,912

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Summary of Fair Value and Carrying Value of Assets and Liabilities Measured on Recurring and Non-recurring Basis	The following table includes the estimated fair value and carrying value of those assets and liabilities that are measured at fair value on a recurring and non-recurring basis as well as the estimated fair value of the Company’s financial instruments that are not accounted for at the fair value on a recurring basis. September 30, 2018 December 31, 2017 Fair Value Hierarchy Level Carrying Amount Asset / (Liability) $ Fair Value Asset / (Liability) $ Carrying Amount Asset / (Liability) $ Fair Value Asset / (Liability) $ Recurring: Cash and cash equivalents and restricted cash Level 1 58,827 58,827 75,710 75,710 Derivative instruments (note 9) Interest rate swap agreements (1) Level 2 8,504 8,504 5,242 5,242 Forward freight agreements (1) Level 2 102 102 — — Other: Advances to equity accounted investments Note (2) 9,930 Note (2) 9,930 Note (2) Long-term debt, including current portion Level 2 (807,078 ) (793,851 ) (952,302 ) (946,105 ) Obligations related to capital leases, including current portion Level 2 (296,710 ) (290,849 ) (148,908 ) (147,401 ) (1) The fair value of the Company’s interest rate swap agreements and FFAs at September 30, 2018 and December 31, 2017 excludes accrued interest income and expenses which are recorded in accounts receivables and accrued liabilities, respectively, on the unaudited consolidated balance sheets. (2) The advances to equity-accounted investments together with the Company’s investments in the equity-accounted investments form the net aggregate carrying value of the Company’s interests in the equity-accounted investments in these consolidated financial statements. The fair values of the individual components of such aggregate interests as at September 30, 2018 and December 31, 2017 were not determinable.
Summary of Financing Receivables	The following table contains a summary of the Company’s financing receivables by type and the method by which the Company monitors the credit quality of its financing receivables on a quarterly basis. September 30, 2018 December 31, 2017 Class of Financing Receivable Credit Quality Indicator Grade $ $ Advances to equity accounted investments Other internal metrics Performing 9,930 9,930 Total 9,930 9,930

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Summary of Related Party Transactions	Amounts received and paid by the Company for such related party transactions for the periods indicated were as follows: Three Months Ended Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 $ $ $ $ RSA pool management fees and commissions (i) — — — (2,799 ) Commercial management fees (ii) — — — (1,187 ) Vessel operating expenses - technical management fee (iii) (2,800 ) (2,020 ) (8,900 ) (6,442 ) Strategic and administrative service fees (iv) (7,875 ) (6,761 ) (25,204 ) (13,678 ) Secondment fees (v) (189 ) (148 ) (548 ) (188 ) LNG service revenues (vi) 72 84 344 252 Technical management fee revenue (vii) 3,490 3,828 9,819 5,048 Service revenues (viii) 343 1,003 758 1,280 Entities under Common Control (note 4) RSA pool management fees and commissions (i) — — — 2,799 Commercial management fees (ii) — — — 1,187 Strategic and administrative service fees (iv) — — — (7,026 ) Technical management fee revenue (vii) — — — 4,890 Service revenues (viii) — — — 1,772 (i) Prior to 2018, the Company’s share of TTOL’s fees for RSAs are reflected as a reduction to net pool revenues on the Company’s consolidated statements of loss. The Company acquired the remaining 50% interest in TTOL on May 31, 2017 (notes 4 and 6 (c)). Subsequent to the acquisition, the Company's share of TTOL's fees has been eliminated. (ii) The Manager’s commercial management fees for vessels on time-charter out contracts and spot-traded vessels that are not included in the RSAs are reflected in voyage expenses on the Company’s consolidated statements of loss. Subsequent to the Company's acquisition of the remaining 50% interest in TTOL, the Company's share of the Manager's commercial management fees has been eliminated. (iii) The cost of ship management services provided by the Manager has been presented as vessel operating expenses on the Company's consolidated statements of loss. (iv) The Manager's strategic and administrative service fees have been presented in general and administrative expenses on the Company's consolidated statements of loss. The Company's executive officers are employees of Teekay or subsidiaries thereof, and their compensation (other than any awards under the Company's long-term incentive plan described in note 12 ) is set and paid by Teekay or such other subsidiaries. The Company reimburses Teekay for time spent by its executive officers on the Company's management matters through the strategic portion of the management fee. (v) The Company pays secondment fees for services provided by some employees of Teekay. Secondment fees have been presented in general and administrative expenses on the Company's consolidated statements of loss. (vi) The Company's ship-to-ship transfer business has an operational and maintenance subcontract with Teekay LNG Bahrain Operations L.L.C., an entity wholly-owned by TGP (which is controlled by Teekay), for the Bahrain LNG Import Terminal (or the Terminal ). The Terminal is owned by Bahrain LNG W.I.L., a joint venture for which Teekay LNG Operating L.L.C., an entity wholly-owned by TGP, has a 30% interest. The Company's ship-to-ship transfer business also has a services agreement with Teekay Shipping Ltd., an entity wholly-owned by Teekay, to provide certain LNG services. (vii) The Company receives reimbursements from Teekay who subcontracts technical management services from the Manager. These reimbursements have been presented in general and administrative expenses on the Company's consolidated statements of loss. (viii) The Company recorded revenue relating to TTOL's administration of certain RSAs and provision of certain commercial services to participants in the arrangements. The Company also recorded revenues of $1.8 million for the nine months ended September 30, 2017 associated with the Entities under Common Control.

Loss Per Share (Tables)

Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Basic and Diluted (Loss) Earnings Per Share	The net loss available for common shareholders and loss per common share presented in the table below includes the results of operations of the Entities under Common Control which were not purchased solely with cash (note 4): Three Months Ended Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 $ $ $ $ Net loss (17,484 ) (22,380 ) (64,050 ) (56,144 ) Weighted average number of common shares – basic (1) 268,558,556 179,224,094 268,470,804 178,853,698 Dilutive effect of stock-based awards — — — — Weighted average number of common shares – diluted (1) 268,558,556 179,224,094 268,470,804 178,853,698 Loss per common share: – Basic (0.07 ) (0.12 ) (0.24 ) (0.31 ) – Diluted (0.07 ) (0.12 ) (0.24 ) (0.31 ) (1) The weighted-average number of common shares outstanding for periods prior to May 2017 has been retroactively adjusted to include approximately 13.8 million shares of the Company's Class B common stock issued to Teekay as consideration for the acquisition of 50% of TTOL in May 2017.

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Total cash, cash equivalents and restricted cash is as follows: As at As at As at As at September 30, 2018 December 31, 2017 September 30, 2017 December 31, 2016 $ $ $ $ Cash and cash equivalents 54,361 71,439 60,606 94,157 Restricted cash – current 1,794 1,599 1,645 750 Restricted cash – long-term 2,672 2,672 2,672 — 58,827 75,710 64,923 94,907

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements Accounting Pronouncements - Narrative (Details) - Accounting Standards Update 2014-09 - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in cost of goods and services sold	$ 73,600,000	$ 202,400,000
Cumulative effect of new accounting principle in period of adoption			$ 0
Increase in other current assets	1,400,000	1,400,000
Decrease In accounts receivable	1,400,000	1,400,000
Voyage charter revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in voyage charter revenue	$ 73,600,000	$ 202,400,000

Revenue Revenue - Narrative (De

Revenue Revenue - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)contractvessel	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Disaggregation of Revenue [Line Items]
Number of forms of contracts | contract			2
Total revenues	$ 175,915	$ 91,238	$ 516,039	$ 330,512
Operating leases, future minimum payments receivable	14,400		14,400
Operating leases, future minimum payments receivable, remainder of fiscal year	8,100		8,100
Operating leases, future minimum payments receivable, in 2 years	6,300		6,300
Property subject to or available for operating lease, net	196,800		196,800		$ 517,900
Property subject to or available for operating lease, gross	303,800		303,800		754,200
Property subject to or available for operating lease, accumulated depreciation	107,000		107,000		236,300
Deferred revenue	89		89		557
Time-charter revenues
Disaggregation of Revenue [Line Items]
Total revenues	12,326	24,681	51,820	85,102
Deferred revenue	100		$ 100		$ 500
High-Q Joint Venture
Disaggregation of Revenue [Line Items]
Number of vessels | vessel			1
High-Q Joint Venture | Time-charter revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 700	$ 1,700	$ 3,400	$ 5,100
Charters Out
Disaggregation of Revenue [Line Items]
Number of vessels | vessel			6
Number of vessels with options to extend | vessel			1
Lessor, operating lease, renewal term			12 months
2018 Time Charter Contract Expiration | Charters Out
Disaggregation of Revenue [Line Items]
Number of vessels | vessel			4
2019 Time Charter Contract Expiration | Charters Out
Disaggregation of Revenue [Line Items]
Number of vessels | vessel			2

Revenue Revenue - Disaggregatio

Revenue Revenue - Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 175,915	$ 91,238	$ 516,039	$ 330,512
Voyage Charters - Suezmax
Disaggregation of Revenue [Line Items]
Total revenues	90,267	271	243,771	12,905
Voyage Charters - Aframax
Disaggregation of Revenue [Line Items]
Total revenues	29,210	4,869	76,952	13,900
Voyage Charters - LR2
Disaggregation of Revenue [Line Items]
Total revenues	16,712	0	40,312	0
Voyage Charters - Full Service Lightering
Disaggregation of Revenue [Line Items]
Total revenues	15,858	20,257	70,982	68,076
Voyage charter revenues
Disaggregation of Revenue [Line Items]
Total revenues	152,047	25,397	432,017	94,881
Time Charters - Aframax
Disaggregation of Revenue [Line Items]
Total revenues	7,784	12,318	31,608	36,975
Time Charters - Suezmax
Disaggregation of Revenue [Line Items]
Total revenues	2,909	9,167	13,063	35,918
Time Charters - LR2
Disaggregation of Revenue [Line Items]
Total revenues	1,633	3,196	7,149	12,209
Time-charter revenues
Disaggregation of Revenue [Line Items]
Total revenues	12,326	24,681	51,820	85,102
Ship-to-ship support services, Other revenue
Disaggregation of Revenue [Line Items]
Total revenues	8,217	7,980	22,452	28,210
Commercial management, Other revenue
Disaggregation of Revenue [Line Items]
Total revenues	2,050	3,112	6,246	9,448
LNG terminal management, consultancy and other, Other revenue
Disaggregation of Revenue [Line Items]
Total revenues	1,275	1,822	3,504	4,336
Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	11,542	12,914	32,202	41,994
Net Pool - Suezmax
Disaggregation of Revenue [Line Items]
Total revenues	0	18,820	0	66,261
Net Pool - Aframax
Disaggregation of Revenue [Line Items]
Total revenues	0	4,832	0	23,195
Net Pool - LR2
Disaggregation of Revenue [Line Items]
Total revenues	0	4,598	0	19,067
Net Pool - MR2
Disaggregation of Revenue [Line Items]
Total revenues	0	(4)	0	12
Net pool revenues
Disaggregation of Revenue [Line Items]
Total revenues	0	$ 28,246	0	$ 108,535
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Increase in cost of goods and services sold	73,600		202,400
Accounting Standards Update 2014-09 | Voyage charter revenues
Disaggregation of Revenue [Line Items]
Increase in voyage charter revenue	$ 73,600		$ 202,400

Acquisition of Entities under_2

Acquisition of Entities under Common Control (Details) - USD ($) $ in Thousands, shares in Millions	May 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Aug. 31, 2014
Business Acquisition [Line Items]
Return of capital				$ 746	$ 0
Net loss		$ (17,484)	$ (22,380)	(64,050)	(56,144)
Total revenues		$ 175,915	$ 91,238	$ 516,039	330,512
Entities Under Common Control | Teekay Tanker Operations Limited
Business Acquisition [Line Items]
Percentage of voting interests acquired	50.00%					50.00%
Purchase price of acquisition	$ 39,000
Ownership percentage after acquisition	100.00%
Net loss					1,300
Total revenues					$ 8,600
Entities Under Common Control | Teekay Tanker Operations Limited | Working Capital
Business Acquisition [Line Items]
Purchase price of acquisition	$ 13,100
Teekay Corporation | Entities Under Common Control | Teekay Tanker Operations Limited
Business Acquisition [Line Items]
Purchase price of acquisition	39,000
Net assets acquired	13,300
Return of capital	25,700
Teekay Corporation | Entities Under Common Control | Teekay Tanker Operations Limited | Working Capital
Business Acquisition [Line Items]
Purchase price of acquisition	$ 13,100
Class B | Teekay Corporation | Entities Under Common Control | Teekay Tanker Operations Limited
Business Acquisition [Line Items]
Number of shares issued (in shares)	13.8

Segment Reporting - Additional

Segment Reporting - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Reporting - Schedule of

Segment Reporting - Schedule of Company's Revenue and Income From Operations by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 175,915	$ 91,238	$ 516,039	$ 330,512
Voyage expenses	(83,048)	(18,303)	(249,974)	(61,488)
Vessel operating expenses	(52,161)	(40,958)	(157,808)	(131,949)
Time-charter hire expense	(4,317)	(5,835)	(14,697)	(27,459)
Depreciation and amortization	(29,595)	(24,328)	(88,598)	(73,652)
General and administrative expenses	(8,747)	(7,622)	(27,939)	(24,875)
(Loss) gain on sale of vessels	0	(7,926)	170	(12,495)
Restructuring charges	(213)	0	(1,195)	0
Loss from operations	(2,166)	(13,734)	(24,002)	(1,406)
Equity loss	(359)	(274)	265	(27,174)
Operating Segments | Conventional Tanker Segment
Segment Reporting Information [Line Items]
Revenues	166,423	81,758	490,083	299,154
Voyage expenses	(85,575)	(20,725)	(259,079)	(69,517)
Vessel operating expenses	(43,432)	(32,227)	(131,886)	(100,586)
Time-charter hire expense	(2,935)	(4,629)	(10,326)	(23,698)
Depreciation and amortization	(28,532)	(23,071)	(85,171)	(69,857)
General and administrative expenses	(7,985)	(6,823)	(25,385)	(22,258)
(Loss) gain on sale of vessels		(7,968)	0	(12,545)
Restructuring charges	0		(152)
Loss from operations	(2,036)	(13,685)	(21,916)	693
Equity loss	(359)	(274)	265	(27,174)
Operating Segments | Ship-to-Ship Transfer Segment
Segment Reporting Information [Line Items]
Revenues	12,019	11,902	35,061	39,387
Voyage expenses	0	0	0	0
Vessel operating expenses	(8,729)	(8,731)	(25,922)	(31,363)
Time-charter hire expense	(1,382)	(1,206)	(4,371)	(3,761)
Depreciation and amortization	(1,063)	(1,257)	(3,427)	(3,795)
General and administrative expenses	(762)	(799)	(2,554)	(2,617)
(Loss) gain on sale of vessels		42	170	50
Restructuring charges	(213)		(1,043)
Loss from operations	(130)	(49)	(2,086)	(2,099)
Equity loss	0	0	0	0
Inter-segment Adjustment
Segment Reporting Information [Line Items]
Revenues	(2,527)	(2,422)	(9,105)	(8,029)
Voyage expenses	2,527	2,422	9,105	8,029
Vessel operating expenses	0	0	0	0
Time-charter hire expense	0	0	0	0
Depreciation and amortization	0	0	0	0
General and administrative expenses	0	0	0	0
(Loss) gain on sale of vessels		0	0	0
Restructuring charges	0		0
Loss from operations	0	0	0	0
Equity loss	$ 0	$ 0	$ 0	$ 0

Segment Reporting - Reconciliat

Segment Reporting - Reconciliation of Total Segment Assets to Total Assets Presented in Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated total assets	$ 2,129,194	$ 2,197,348
Cash and cash equivalents	54,361	71,439	$ 60,606	$ 94,157
Conventional Tanker Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated total assets	2,036,698	2,089,099
Ship-to-Ship Transfer Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Consolidated total assets	$ 38,135	$ 36,810

Investments in and Advances t_3

Investments in and Advances to Equity Accounted Investments - Schedule of Investments in and Advances to Equity Accounted Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Investment in and advances to equity accounted investments	$ 24,811	$ 25,460
High-Q Joint Venture
Schedule of Equity Method Investments [Line Items]
Investment in and advances to equity accounted investments	24,811	24,546
Gemini Tankers L.L.C.
Schedule of Equity Method Investments [Line Items]
Investment in and advances to equity accounted investments	$ 0	$ 914

Investments in and Advances t_4

Investments in and Advances to Equity Accounted Investments - Additional Information (Details) $ in Thousands	Nov. 27, 2017USD ($)	May 31, 2017USD ($)poolshares	Jan. 31, 2014USD ($)membershares	Jun. 30, 2017USD ($)	Sep. 30, 2018USD ($)vessel	Dec. 31, 2017USD ($)	Aug. 31, 2014
Investments in and Advances to Affiliates [Line Items]
Total principal					$ 814,709	$ 963,247
Tanker Investments Ltd.
Investments in and Advances to Affiliates [Line Items]
Ownership percentage	11.30%
Number of shares acquiring (in shares) | shares		27,000,000
Class A | Tanker Investments Ltd.
Investments in and Advances to Affiliates [Line Items]
Share for share exchange (in shares) | shares		3.3
Entities Under Common Control | Teekay Tanker Operations Limited
Investments in and Advances to Affiliates [Line Items]
Purchase price of acquisition		$ 39,000
Original ownership interest percentage		50.00%					50.00%
Entities Under Common Control | Teekay Tanker Operations Limited | Working Capital
Investments in and Advances to Affiliates [Line Items]
Purchase price of acquisition		$ 13,100
High-Q Joint Venture
Investments in and Advances to Affiliates [Line Items]
Ownership percentage					50.00%
Tanker Investments Ltd.
Investments in and Advances to Affiliates [Line Items]
Number of shares acquiring (in shares) | shares		27,000,000
High-Q Joint Venture
Investments in and Advances to Affiliates [Line Items]
Number of vessels | vessel					1
Total principal					$ 38,700	$ 42,700
Percentage of exposure to loan guarantee					50.00%
High-Q Joint Venture | Joint Venture Interest Rate Derivative
Investments in and Advances to Affiliates [Line Items]
Fixed interest rate					1.47%
Tanker Investments Ltd.
Investments in and Advances to Affiliates [Line Items]
Ownership percentage		11.30%
Investment in equity accounted investment			$ 25,000
Number of board members to elect | member			1
Tanker Investments Ltd. | Maximum
Investments in and Advances to Affiliates [Line Items]
Number of shares available through exercise of stock purchase warrant (in shares) | shares			750,000
Tanker Investments Ltd. | Common Stock
Investments in and Advances to Affiliates [Line Items]
Common stock, shares purchased (in shares) | shares			2,500,000
Tanker Investments Ltd. | Preferred Stock
Investments in and Advances to Affiliates [Line Items]
Common stock, shares purchased (in shares) | shares			1
Teekay Tanker Operations Limited
Investments in and Advances to Affiliates [Line Items]
Number of commercially managed tanker pools | pool		4
Original ownership interest percentage		50.00%
Teekay Tanker Operations Limited | TTOL
Investments in and Advances to Affiliates [Line Items]
Equity method investment, remaining ownership percentage		50.00%
Tanker Investments Ltd.
Investments in and Advances to Affiliates [Line Items]
Investment write down				$ 28,100
Equity method investment, realized gain (loss) on disposal	$ 1,400

Long-Term Debt - Summary of Lon

Long-Term Debt - Summary of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total principal	$ 814,709	$ 963,247
Less: unamortized discount and debt issuance costs	(7,631)	(10,945)
Total debt	807,078	952,302
Less: current portion	(103,843)	(166,745)
Non-current portion of long-term debt	703,235	785,557
Term Loans
Debt Instrument [Line Items]
Total principal	348,946	423,512
Revolving Credit Facility
Debt Instrument [Line Items]
Total principal	$ 465,763	$ 539,735

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information - Revolvers and Term Loans (Details)	1 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017USD ($)credit_facility	Sep. 30, 2018USD ($)loancredit_facilityvessel	Dec. 31, 2017USD ($)	Jan. 31, 2016USD ($)
Debt Instrument [Line Items]
Total principal	$ 963,247,000	$ 814,709,000	$ 963,247,000
Secured Debt Two | Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Debt term		6 months
Maintain the greater of free cash liquidity		$ 100,000,000
Minimum liquidity as a percentage of debt		7.50%
Term Loans
Debt Instrument [Line Items]
Total principal	423,512,000	$ 348,946,000	423,512,000
Remaining Secured Debt | Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Maintain the greater of free cash liquidity		$ 50,000,000
Minimum liquidity as a percentage of debt		5.00%
Term Loan Due 2021 | Term Loans
Debt Instrument [Line Items]
Number of debt instruments | credit_facility		3
Total principal	$ 423,500,000	$ 348,900,000	$ 423,500,000
Debt instrument, interest rate, stated percentage	5.40%	5.40%	5.40%
Maturing in May 2021 | Term Loans
Debt Instrument [Line Items]
Number of debt instruments | loan		2
Revolver 2,017
Debt Instrument [Line Items]
Number of debt instruments | credit_facility	2
Debt instrument, face amount	$ 270,000,000		$ 270,000,000
Repayments of debt	$ 215,800,000
Collateral, number of vessels | vessel		8
Minimum hull coverage ratios		125.00%
Actual hull coverage ratio	191.00%	174.00%	191.00%
Revolver 2017 | Not Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Minimum liquidity covenant requirement		$ 35,000,000
Minimum liquidity as a percentage of consolidated debt covenant requirement		5.00%
2016 Debt Facility
Debt Instrument [Line Items]
Debt instrument, face amount				$ 894,400,000
Collateral, number of vessels | vessel		29
Minimum hull coverage ratios		125.00%
Actual hull coverage ratio	145.00%	134.00%	145.00%
2016 Debt Facility | Not Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Minimum liquidity covenant requirement		$ 35,000,000
Minimum liquidity as a percentage of consolidated debt covenant requirement		5.00%
Remaining Revolving Credit Facilities Maturing in November 2018 | Revolving Credit Facility
Debt Instrument [Line Items]
Total principal		$ 47,600,000
Remaining Secured Debt | Term Loans
Debt Instrument [Line Items]
Number of debt instruments | credit_facility		2
Collateral, number of vessels | vessel		6
Minimum
Debt Instrument [Line Items]
Percentage of margin		0.30%
Minimum | Revolver 2017 | Not Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Debt term		6 months
Minimum | 2016 Debt Facility | Not Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Debt term		6 months
Maximum
Debt Instrument [Line Items]
Percentage of margin		2.75%
LIBOR | Minimum | Term Loans
Debt Instrument [Line Items]
Percentage of margin		0.30%	0.30%
LIBOR | Maximum | Term Loans
Debt Instrument [Line Items]
Percentage of margin		2.00%	2.00%
Revolving Credit Facility
Debt Instrument [Line Items]
Total principal	$ 539,735,000	$ 465,763,000	$ 539,735,000
Revolving Credit Facility | Revolving Credit Facilities Due through 2022
Debt Instrument [Line Items]
Number of debt instruments | credit_facility		3
Revolving credit facilities borrowing capacity	628,300,000	$ 500,600,000	628,300,000
Undrawn amount of revolving credit facility	$ 88,600,000	34,800,000	$ 88,600,000
Long-term debt, maturities, revolving credit facility, decrease in amount available remaining fiscal year		51,400,000
Long-term debt, maturities, revolving credit facility, decrease in amount available, year 2		19,200,000
Long-term debt, maturities, revolving credit facility, decrease in amount available, year 3		19,200,000
Long-term debt, maturities, revolving credit facility, decrease in amount available, year 4		311,900,000
Long-term debt, maturities, revolving credit facility, decrease in amount available, year 5		$ 98,900,000
Revolving Credit Facility | Remaining Revolving Credit Facilities Maturing in November 2018
Debt Instrument [Line Items]
Collateral, number of vessels | vessel		3
Minimum hull coverage ratios		105.00%
Actual hull coverage ratio	118.00%	150.00%	118.00%
Revolving Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Percentage of margin		2.00%	0.45%
Revolving Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Percentage of margin		2.75%	2.75%
Remaining Revolving Credit Facilities | Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Maintain the greater of free cash liquidity		$ 50,000,000
Minimum liquidity as a percentage of debt		5.00%
Remaining Revolving Credit Facilities | Minimum | Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Debt term		6 months
Remaining Secured Debt | Minimum | Guaranteed By Teekay Corporation
Debt Instrument [Line Items]
Debt term		6 months

Long Term Debt - Additional Inf

Long Term Debt - Additional Information - Other (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Instruments [Abstract]
Weighted-average effective interest rate	4.30%	3.50%
Aggregate annual long-term principal repayments, remainder of 2018	$ 25.9
Aggregate annual long-term principal repayments, 2019	104.6
Aggregate annual long-term principal repayments, 2020	120.9
Aggregate annual long-term principal repayments, 2021	426.8
Aggregate annual long-term principal repayments, 2022	102.5
Aggregate annual long-term principal repayments, after 2022	$ 34

Leases - Capital Lease Obligati

Leases - Capital Lease Obligation (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Capital Leased Assets [Line Items]
Total obligations related to capital leases	$ 296,710	$ 148,908
Less: current portion	(15,839)	(7,227)
Long-term obligations related to capital leases	280,871	141,681
Aframax Tanker
Capital Leased Assets [Line Items]
Total obligations related to capital leases	153,140	0
Suezmax Tankers
Capital Leased Assets [Line Items]
Total obligations related to capital leases	$ 143,570	$ 148,908

Leases - Additional Information

Leases - Additional Information (Details)	1 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)vessel	Jul. 31, 2017USD ($)vessel	Sep. 30, 2017vessel	Sep. 30, 2018USD ($)vessel	Sep. 30, 2017USD ($)vessel	Dec. 31, 2017
Capital Leased Assets [Line Items]
Proceeds from financing related to sales and leaseback of vessels | $				$ 156,644,000	$ 153,000,000
Aframax Tanker
Capital Leased Assets [Line Items]
Actual hull coverage ratio	89.00%			89.00%		0.00%
Suezmax Tankers
Capital Leased Assets [Line Items]
Actual hull coverage ratio	100.00%			100.00%		105.00%
Minimum | Suezmax and Aframax Tankers
Capital Leased Assets [Line Items]
Sale-leaseback, term of contract				9 years
Maximum | Suezmax and Aframax Tankers
Capital Leased Assets [Line Items]
Sale-leaseback, term of contract				12 years
Option to Purchase July 2020-2029 | Suezmax Tankers
Capital Leased Assets [Line Items]
Debt covenant minimum hull coverage ratio, Years 1, 2 and 3				90.00%
Period required to maintain 90% hull coverage ratio				3 years
Minimum hull coverage ratios, thereafter				100.00%
Option to Purchase September 2020 to End of Term | Aframax Tanker
Capital Leased Assets [Line Items]
Minimum hull coverage ratios, thereafter				90.00%
Debt covenant minimum hull coverage ratio, Year 1				75.00%
Debt covenant minimum hull coverage ratio, Year 2				78.00%
Debt covenant minimum hull coverage ratio, Years 3 and 4				80.00%
Capital Lease | Suezmax and Aframax Tankers
Capital Leased Assets [Line Items]
Minimum liquidity covenant requirement | $	$ 35,000,000			$ 35,000,000
Minimum liquidity as a percentage of consolidated debt covenant requirement	5.00%			5.00%
Number of capital leases | vessel				10
Commitments under the capital leases | $	$ 445,300,000			$ 445,300,000
Imputed interest | $	148,600,000			$ 148,600,000
Capital Lease | Minimum | Suezmax and Aframax Tankers
Capital Leased Assets [Line Items]
Debt term				6 months
Aframax Tanker
Capital Leased Assets [Line Items]
Proceeds from financing related to sales and leaseback of vessels | $	156,600,000
Number of vessels sold | vessel			3		3
Suezmax Tankers
Capital Leased Assets [Line Items]
Proceeds from financing related to sales and leaseback of vessels | $		$ 153,000,000
Number of vessels sold | vessel			2		2
Aframax Tankers Sale Leaseback
Capital Leased Assets [Line Items]
Proceeds from financing related to sales and leaseback of vessels | $	$ 156,600,000
Number of vessels sold | vessel	6
Aframax Tankers Sale Leaseback | Option to Purchase September 2020 to End of Term | Aframax Tanker
Capital Leased Assets [Line Items]
Number of vessels | vessel				6
Suezmax Tanker Sale Leaseback
Capital Leased Assets [Line Items]
Proceeds from financing related to sales and leaseback of vessels | $		$ 153,000,000
Suezmax Tanker Sale Leaseback | Option to Purchase July 2020-2029 | Suezmax Tankers
Capital Leased Assets [Line Items]
Number of vessels | vessel				4
Number of vessels sold | vessel		4
Suezmax Tanker Sale Leaseback | Suezmax Tankers
Capital Leased Assets [Line Items]
Number of vessels sold | vessel		4

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) - Suezmax and Aframax Tankers $ in Thousands	Sep. 30, 2018USD ($)
Year
Remaining 2,018	$ 9,574
2,019	37,954
2,020	38,052
2,021	37,943
2,022	37,936
Thereafter	$ 283,836

Derivative Instruments - Summar

Derivative Instruments - Summary of Interest Rate Swap Positions (Details)	9 Months Ended
	Sep. 30, 2018USD ($)
Minimum
LIBOR-Based Debt:
Margin on variable-rate debt	0.30%
Maximum
LIBOR-Based Debt:
Margin on variable-rate debt	2.75%
U.S. Dollar-denominated interest rate swap 1
LIBOR-Based Debt:
Notional Amount	$ 104,133,000
Fair Value / Carrying Amount of Asset	$ 1,770,000
Remaining Term	2 years 3 months 18 days
Fixed Interest Rate	1.46%
U.S. Dollar-denominated interest rate swap 2
LIBOR-Based Debt:
Notional Amount	$ 150,000,000
Fair Value / Carrying Amount of Asset	$ 4,720,000
Remaining Term	2 years 3 months 18 days
Fixed Interest Rate	1.55%
U.S. Dollar-denominated interest rate swap 3
LIBOR-Based Debt:
Notional Amount	$ 50,000,000
Fair Value / Carrying Amount of Asset	$ 2,014,000
Remaining Term	2 years 3 months 18 days
Fixed Interest Rate	1.16%

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Details)	May 01, 2017	Jun. 01, 2016USD ($)vessel	Sep. 30, 2018shares	Dec. 31, 2017shares	Jan. 31, 2014shares
Time-charter swap agreement
Derivative [Line Items]
Aframax equivalent vessel percent		55.00%
Derivative, number of vessel-equivalents in swap agreement | vessel		2
Agreement daily receivable | $		$ 27,776
Derivative, brokerage fee, percent		1.25%
Derivative, deduction from daily payments made | $		$ 500
Derivative, term of contract (in months)		11 months
Derivative, term of contract extension, counterparty option (in months)	2 months	2 months
Tanker Investments Ltd. | Maximum
Derivative [Line Items]
Number of shares available through exercise of stock purchase warrant (in shares)					750,000
Tanker Investments Ltd. | Stock purchase warrant
Derivative [Line Items]
Number of stock purchase warrants (in warrants)				1
Tanker Investments Ltd. | Stock purchase warrant | Maximum
Derivative [Line Items]
Number of shares available through exercise of stock purchase warrant (in shares)			750,000

Derivative Instruments - Locati

Derivative Instruments - Location and Fair Value Amounts of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Current portion of derivative assets	$ 3,075	$ 1,016
Derivative assets	5,531	4,226
Carrying Amount Asset / (Liability)
Derivatives, Fair Value [Line Items]
Current portion of derivative assets	3,075	1,016
Derivative assets	5,531	4,226
Accounts receivables (Accrued liabilities)	390	(39)
Carrying Amount Asset / (Liability) | Interest rate swap agreements
Derivatives, Fair Value [Line Items]
Current portion of derivative assets	2,973	1,016
Derivative assets	5,531	4,226
Accounts receivables (Accrued liabilities)	394	$ (39)
Carrying Amount Asset / (Liability) | Forward freight agreements
Derivatives, Fair Value [Line Items]
Current portion of derivative assets	102
Accounts receivables (Accrued liabilities)	$ (4)

Derivative Instruments - Gain (

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

Other Expense - Components of O

Other Expense - Components of Other Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Liabilities Disclosure [Abstract]
Freight tax provision	$ (2,050)	$ (1,864)	$ (10,014)	$ (6,296)
Foreign exchange gain	1,251	81	6,025	151
Other income	0	15	49	227
Total	$ (799)	$ (1,768)	$ (3,940)	$ (5,918)

Other Expense - Schedule of Unr

Other Expense - Schedule of Unrecognized Tax Benefits (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance of unrecognized tax benefits as at January 1	$ 26,054
Increases for positions related to the current period	2,099
Changes for positions taken in prior periods	1,852
Decreases related to statute of limitations	(93)
Balance of unrecognized tax benefits as at September 30	$ 29,912

Financial Instruments - Summary

Financial Instruments - Summary of Fair Value and Carrying Value of Assets and Liabilities Measured on Recurring and Non-recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents and restricted cash	$ 58,827	$ 75,710	$ 64,923	$ 94,907
Derivative assets	5,531	4,226
Advances to equity accounted investments	9,930	9,930
Long-term debt, including current portion	(807,078)	(952,302)
Obligations related to capital leases, including current portion	(296,710)	(148,908)
Carrying Amount Asset / (Liability)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	5,531	4,226
Carrying Amount Asset / (Liability) | Advances to equity accounted investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Advances to equity accounted investments	9,930	9,930
Carrying Amount Asset / (Liability) | Interest rate swap agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	5,531	4,226
Carrying Amount Asset / (Liability) | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current portion	(807,078)	(952,302)
Obligations related to capital leases, including current portion	(296,710)	(148,908)
Carrying Amount Asset / (Liability) | Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents and restricted cash	58,827	75,710
Carrying Amount Asset / (Liability) | Recurring | Level 2 | Interest rate swap agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements	8,504	5,242
Carrying Amount Asset / (Liability) | Recurring | Level 2 | Forward freight agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	102	0
Fair Value Asset / (Liability) | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current portion	(793,851)	(946,105)
Obligations related to capital leases, including current portion	(290,849)	(147,401)
Fair Value Asset / (Liability) | Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents and restricted cash	58,827	75,710
Fair Value Asset / (Liability) | Recurring | Level 2 | Interest rate swap agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements	8,504	5,242
Fair Value Asset / (Liability) | Recurring | Level 2 | Forward freight agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	$ 102	$ 0

Financial Instruments - Summa_2

Financial Instruments - Summary of Financing Receivables (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Advances to equity accounted investments	$ 9,930	$ 9,930
Other internal metrics | Performing
Financing Receivable, Recorded Investment [Line Items]
Advances to equity accounted investments	$ 9,930	$ 9,930

Capital Stock and Stock-Based_2

Capital Stock and Stock-Based Compensation (Details) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares	Mar. 31, 2017USD ($)$ / sharesshares	Sep. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)vote$ / sharesshares	Sep. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2017$ / sharesshares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)			100,000,000		100,000,000		100,000,000
Preferred stock, par value (usd per share) | $ / shares			$ 0.01		$ 0.01		$ 0.01
Common stock, shares authorized (in shares)			585,000,000		585,000,000		385,000,000
Preferred stock, shares issued (in shares)			0		0		0
Preferred stock, shares outstanding (in shares)			0		0		0
Stock based compensation expense | $			$ 0.2	$ 0.2	$ 0.8	$ 0.8
Restricted Stock Units
Class of Stock [Line Items]
Restricted stock units vested (in shares)					300,000	300,000
Market value of restricted stock units | $					$ 0.3	$ 0.6
2007 Long-Term Incentive Plan | Stock Options
Class of Stock [Line Items]
Weighted-average grant date fair value of stock options granted (usd per share) | $ / shares					$ 0.35	$ 0.67
Expected volatility rate					48.70%	50.20%
Expected life (in years)					5 years	5 years
Dividend yield					5.50%	5.00%
Risk-free interest rate					2.60%	2.10%
Period of historical sata used to calculate expected volatility in year					5 years
2007 Long-Term Incentive Plan | Non Management Directors | Stock Options
Class of Stock [Line Items]
Stock options granted during period (in shares)	500,000	400,000
Exercise price of stock options granted (usd per share) | $ / shares	$ 1.22	$ 2.23
Term of stock options (in years)					10 years
2007 Long-Term Incentive Plan | Officer | Stock Options
Class of Stock [Line Items]
Stock options granted during period (in shares)	700,000	500,000
Exercise price of stock options granted (usd per share) | $ / shares	$ 1.22	$ 2.23
Term of stock options (in years)					10 years
Vesting period (in years)					3 years
2007 Long-Term Incentive Plan | Officers and Certain Subsidiaries Employees | Restricted Stock Units
Class of Stock [Line Items]
Vesting period (in years)					3 years
Common stock, granted (in shares)	800,000	400,000
Common stock aggregate values, granted | $	$ 0.9	$ 0.8
Conversion basis (in shares)					1
Class A
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			485,000,000		485,000,000		285,000,000
Common stock, par value (usd per share) | $ / shares			$ 0.01		$ 0.01		$ 0.01
Common Stock, voting rights, votes per share owned | vote					1
Common stock, shares issued (in shares)			231,600,000		231,600,000		231,200,000
Common stock, shares outstanding (in shares)			231,600,000		231,600,000		231,200,000
Class A | Restricted Stock Units
Class of Stock [Line Items]
Number of shares issued (in shares)					200,000	200,000
Class A | 2007 Long-Term Incentive Plan | Non Management Directors
Class of Stock [Line Items]
Shares issued in period (in shares)	168,029
Stock issued in period, gross | $	$ 0.2
Class B
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			100,000,000		100,000,000		100,000,000
Common stock, par value (usd per share) | $ / shares			$ 0.01		$ 0.01		$ 0.01
Common Stock, voting rights, votes per share owned | vote					5
Maximum percentage of voting power					49.00%
Common stock, shares issued (in shares)			37,000,000		37,000,000		37,000,000
Common stock, shares outstanding (in shares)			37,000,000		37,000,000		37,000,000
General and Administrative Expense | Class A
Class of Stock [Line Items]
Stock based compensation expense | $					$ 0.4	$ 0.3

Related Party Transactions - Su

Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	May 31, 2017	Nov. 30, 2016	Aug. 31, 2014
Related Party Transaction [Line Items]
RSA pool management fees and commissions	$ 0	$ 0	$ 0	$ (2,799)
Commercial management fees	0	0	0	(1,187)
Vessel operating expenses	(52,161)	(40,958)	(157,808)	(131,949)
Strategic and administrative service fees	(7,875)	(6,761)	(25,204)	(13,678)
Revenues	175,915	91,238	516,039	330,512
Teekay LNG Operating L.L.C. | Bahrain LNG W.I.L.
Related Party Transaction [Line Items]
Ownership percentage						30.00%
Entities Under Common Control
Related Party Transaction [Line Items]
RSA pool management fees and commissions	0	0	0	2,799
Commercial management fees	0	0	0	1,187
Strategic and administrative service fees	0	0	0	(7,026)
Vessel operating expenses - technical management fee
Related Party Transaction [Line Items]
Vessel operating expenses	(2,800)	(2,020)	(8,900)	(6,442)
Secondment fees
Related Party Transaction [Line Items]
Strategic and administrative service fees	(189)	(148)	(548)	(188)
LNG terminal services revenue
Related Party Transaction [Line Items]
Revenues	72	84	344	252
Technical management fee revenues
Related Party Transaction [Line Items]
Revenues	3,490	3,828	9,819	5,048
Technical management fee revenues | Entities Under Common Control
Related Party Transaction [Line Items]
Revenues	0	0	0	4,890
Service revenues
Related Party Transaction [Line Items]
Revenues	343	1,003	758	1,280
Service revenues | Entities Under Common Control
Related Party Transaction [Line Items]
Revenues	$ 0	$ 0	$ 0	1,772
Teekay Tanker Operations Limited | Entities Under Common Control
Related Party Transaction [Line Items]
Revenues				$ 8,600
Percentage of voting interests acquired					50.00%		50.00%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Working capital advanced to Pool Managers	$ 50,551		$ 50,551		$ 49,103
Revenue Sharing Arrangements
Related Party Transaction [Line Items]
Working capital advanced to Pool Managers	48,300		48,300		$ 45,100
Aframax Tanker | RSA Participants | Vessels Hire
Related Party Transaction [Line Items]
Amounts of transaction	$ 3,300	$ 2,900	$ 19,100	$ 10,300

Sales of Vessels (Details)

Sales of Vessels (Details) $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Nov. 30, 2018USD ($)vessel	Sep. 30, 2018USD ($)vessel	Jul. 31, 2017USD ($)vessel	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)vessel	Sep. 30, 2018USD ($)vessel	Sep. 30, 2017USD ($)vessel
Property, Plant and Equipment [Line Items]
(Loss) gain on sale of vessels (note 14) | $				$ 0	$ (7,926)	$ 170	$ (12,495)
Proceeds from financing related to sales and leaseback of vessels | $						156,644	$ 153,000
Ship-to-ship Support Vessel
Property, Plant and Equipment [Line Items]
(Loss) gain on sale of vessels (note 14) | $						$ 200
Number of vessels sold | vessel					1	1	1
Aframax Tanker
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel					3		3
Proceeds from financing related to sales and leaseback of vessels | $		$ 156,600
Suezmax Tankers
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel					2		2
Proceeds from financing related to sales and leaseback of vessels | $			$ 153,000
Suezmax, Aframax and Ship-to-ship Support Vessels
Property, Plant and Equipment [Line Items]
(Loss) gain on sale of vessels (note 14) | $					$ (7,900)		$ (12,500)
Subsequent Event | Suezmax, Aframax and LR2 Vessels
Property, Plant and Equipment [Line Items]
Proceeds from financing related to sales and leaseback of vessels | $	$ 84,700
Aframax Tankers Sale Leaseback
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel		6
Proceeds from financing related to sales and leaseback of vessels | $		$ 156,600
Aframax Tankers Sale Leaseback | Subsequent Event | Aframax Tanker
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel	2
Suezmax, Aframax and LR2 Sale Leaseback | Subsequent Event
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel	4
Suezmax Tanker Sale Leaseback
Property, Plant and Equipment [Line Items]
Proceeds from financing related to sales and leaseback of vessels | $			$ 153,000
Suezmax Tanker Sale Leaseback | Suezmax Tankers
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel			4
Suezmax Tanker Sale Leaseback | Subsequent Event | Suezmax Tankers
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel	1
LR2 Product Tanker Sale Leaseback | Subsequent Event | LR2 Tankers
Property, Plant and Equipment [Line Items]
Number of vessels sold | vessel	1

(Loss) Earnings Per Share - Bas

(Loss) Earnings Per Share - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	May 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Aug. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss		$ (17,484)	$ (22,380)	$ (64,050)	$ (56,144)
Weighted average number of common shares – basic (in shares)		268,558,556	179,224,094	268,470,804	178,853,698
Dilutive effect of stock-based awards (in shares)		0	0	0	0
Weighted average number of common shares – diluted (in shares)		268,558,556	179,224,094	268,470,804	178,853,698
Loss per common share:
– Basic (usd per share)		$ (0.07)	$ (0.12)	$ (0.24)	$ (0.31)
– Diluted (usd per share)		$ (0.07)	$ (0.12)	$ (0.24)	$ (0.31)
Teekay Tanker Operations Limited | Entities Under Common Control
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss					$ 1,300
Loss per common share:
Percentage of voting interests acquired	50.00%					50.00%
Teekay Tanker Operations Limited | Teekay Corporation | Entities Under Common Control | Class B
Loss per common share:
Number of shares issued (in shares)	13,800,000

(Loss) Earnings Per Share - Add

(Loss) Earnings Per Share - Additional Information (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive effect on calculation of diluted earnings per common share attributable to outstanding stock-based awards (in shares)	0.3	0.6	0.3	0.3
Options | Class A
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive effect on calculation of diluted earnings per common share attributable to outstanding stock-based awards (in shares)	2.9	1.7	2.9	1.6

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 54,361	$ 71,439	$ 60,606	$ 94,157
Restricted cash – current	1,794	1,599	1,645	750
Restricted cash – long-term	2,672	2,672	2,672	0
Cash and cash equivalents and restricted cash	$ 58,827	$ 75,710	$ 64,923	$ 94,907

Liquidity Liquidity - Additiona

Liquidity Liquidity - Additional information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total principal	$ 814,709	$ 963,247
Revolving Credit Facility | Remaining Revolving Credit Facilities Maturing in 4Q 2018
Debt Instrument [Line Items]
Total principal	$ 47,600

Acquisition of Tanker Investm_2

Acquisition of Tanker Investments Ltd. (Details) $ / shares in Units, $ in Thousands	Nov. 27, 2017USD ($)vessel$ / sharesshares	May 31, 2017shares	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Business Acquisition [Line Items]
Proceeds from issuance of Class A common stock (note 12)			$ 0	$ 5,000
Tanker Investments Ltd.
Business Acquisition [Line Items]
Number of shares acquiring (in shares) | shares		27,000,000
Proceeds from issuance of Class A common stock (note 12)	$ 151,300
Business acquisition, share price (USD per share) | $ / shares	$ 1.70
Business combination, recognized identifiable assets acquired and liabilities assumed, liabilities, excluding banking debt	$ 47,100
Secured debt	338,900
Business acquisition, transaction costs	$ 6,900
Ownership percentage	11.30%
Business combination, step acquisition, equity interest in acquiree, fair value	$ 19,200
Business combination, consideration transferred, including equity interest in acquiree held prior to combination	177,400
Business combination, recognized identifiable assets acquired and liabilities assumed, noncurrent liabilities, long-term debt	337,100
Business combination, recognized identifiable assets acquired and liabilities assumed, property, plant, and equipment	467,200
Business combination, recognized identifiable assets acquired and liabilities assumed, operating lease	$ 200
Tanker Investments Ltd. | Class A
Business Acquisition [Line Items]
Share for share exchange (in shares) | shares		3.3
Number of shares issued (in shares) | shares	88,977,544
Suezmax Tankers | Tanker Investments Ltd.
Business Acquisition [Line Items]
Number of vessels | vessel	10
Aframax Tanker | Tanker Investments Ltd.
Business Acquisition [Line Items]
Number of vessels | vessel	6
Long Range 2 | Tanker Investments Ltd.
Business Acquisition [Line Items]
Number of vessels | vessel	2
Vessels | Tanker Investments Ltd.
Business Acquisition [Line Items]
Business combination, average age of acquired property	7 years 3 months 19 days

Shipbuilding Contracts - Additi

Shipbuilding Contracts - Additional Information (Detail) t in Thousands	Feb. 15, 2016USD ($)subsidiary	Jun. 30, 2018shares	Nov. 30, 2017	Apr. 30, 2013contractvesselsubsidiaryt	Sep. 30, 2018USD ($)
Property, Plant and Equipment [Line Items]
Number of special purpose subsidiaries | subsidiary	4			4
STX Offshore And Shipbuilding Co., Ltd
Property, Plant and Equipment [Line Items]
Weight capacity | t				113
Number of shipbuilding contracts | contract				4
Litigation settlement, amount awarded from other party | $	$ 8,900,000
Litigation settlement, amount receivable in cash, in percent			7.00%
Litigation settlement, amount received in equity, in percent			93.00%
Number of shares awarded in rehabilitation plan (in shares) | shares		315,856
Value of shares acquired in bankruptcy | $					$ 0
STX Offshore And Shipbuilding Co., Ltd | Orders to Construct Newbuildings
Property, Plant and Equipment [Line Items]
Number of vessels | contract				4
STX Offshore And Shipbuilding Co., Ltd | Additional Order Option Maximum
Property, Plant and Equipment [Line Items]
Number of vessels | vessel				12

Subsequent Events (Details)

Subsequent Events (Details)	1 Months Ended			9 Months Ended
	Nov. 30, 2018USD ($)vessel	Sep. 30, 2018USD ($)	Jul. 31, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Subsequent Event [Line Items]
Proceeds from financing related to sales and leaseback of vessels (note 8)				$ 156,644,000	$ 153,000,000
Total principal		$ 814,709,000		814,709,000		$ 963,247,000
Remaining Revolving Credit Facilities Maturing in 4Q 2018 | Revolving Credit Facility
Subsequent Event [Line Items]
Total principal		47,600,000		$ 47,600,000
Aframax Tankers Sale Leaseback
Subsequent Event [Line Items]
Proceeds from financing related to sales and leaseback of vessels (note 8)		$ 156,600,000
Suezmax Tanker Sale Leaseback
Subsequent Event [Line Items]
Proceeds from financing related to sales and leaseback of vessels (note 8)			$ 153,000,000
Subsequent Event | Working Capital Borrowing Base
Subsequent Event [Line Items]
Revolving credit facilities borrowing capacity	$ 40,000,000
Increase in liquidity	20,000,000
Subsequent Event | November 2018 Sale-leaseback Transaction
Subsequent Event [Line Items]
Proceeds from financing related to sales and leaseback of vessels (note 8)	$ 84,700,000
Number of vessels | vessel	4
Subsequent Event | Minimum | November 2018 Sale-leaseback Transaction
Subsequent Event [Line Items]
Sale-leaseback, term of contract	10 years
Fixed time charter rate	$ 5,000
Subsequent Event | Maximum | November 2018 Sale-leaseback Transaction
Subsequent Event [Line Items]
Sale-leaseback, term of contract	12 years
Fixed time charter rate	$ 7,800
Aframax Tanker | Teekay Tankers | Subsequent Event | Aframax Tankers Sale Leaseback
Subsequent Event [Line Items]
Number of vessels | vessel	2
Suezmax Tankers | Teekay Tankers | Subsequent Event | Suezmax Tanker Sale Leaseback
Subsequent Event [Line Items]
Number of vessels | vessel	1
LR2 Tankers | Teekay Tankers | Subsequent Event | LR2 Product Tanker Sale Leaseback
Subsequent Event [Line Items]
Number of vessels | vessel	1