International Seaways (INSW) 10-Q 9 Aug 21 2021 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 05, 2021
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2021
Entity Registrant Name	INTERNATIONAL SEAWAYS, INC.
Entity Incorporation, State or Country Code	1T
Entity File Number	1-37836-1
Entity Tax Identification Number	98-0467117
Entity Address, Address Line One	600 Third Avenue
Entity Address, Address Line Two	39th Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10016
City Area Code	212
Local Phone Number	578-1600
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		50,674,393
Entity Central Index Key	0001679049
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2021
Amendment Flag	false
Common Stock [Member]
Title of 12(b) Security	Common Stock (no par value)
Trading Symbol	INSW
Security Exchange Name	NYSE
8.5% Senior Notes [Member]
Title of 12(b) Security	8.5% Senior Notes due 2023
Trading Symbol	INSW - PA
Security Exchange Name	NYSE

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 117,391	$ 199,390
Voyage receivables, net of allowance for credit losses of $95 and $55 including unbilled of $47,740 and $38,430	50,981	43,362
Other receivables	6,324	4,479
Inventories	2,103	3,601
Prepaid expenses and other current assets	6,365	6,002
Vessel held for sale	29,146	0
Total Current Assets	212,310	256,834
Restricted cash	16,173	16,287
Vessels and other property, less accumulated depreciation of $209,090 and $186,084	1,055,747	1,108,214
Vessels construction in progress	14,606	0
Deferred drydock expenditures, net	39,405	36,334
Operating lease right-of-use assets	16,999	21,588
Investments in and advances to affiliated companies	149,580	141,924
Long-term derivative assets	6,526	2,129
Other assets	7,519	3,229
Total Assets	1,518,865	1,586,539
Current Liabilities:
Accounts payable, accrued expenses and other current liabilities	29,453	34,425
Current portion of operating lease liabilities	7,226	8,867
Current installments of long-term debt	61,483	61,483
Current portion of derivative liabilities	3,950	4,121
Total Current Liabilities	102,112	108,896
Long-term operating lease liabilities	7,541	10,253
Long-term debt	444,566	474,332
Long-term derivative liabilities	3,782	6,155
Other liabilities	13,410	14,861
Total Liabilities	571,411	614,497
Commitments and contingencies
Equity:
Capital - 100,000,000 no par value shares authorized; 28,128,298 and 28,014,877 shares issued and outstanding	1,278,365	1,280,501
Accumulated deficit	(307,994)	(275,846)
Stockholders Equity Subtotal	970,371	1,004,655
Accumulated other comprehensive loss	(22,917)	(32,613)
Total Equity	947,454	972,042
Total Liabilities and Equity	$ 1,518,865	$ 1,586,539

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
CONDENSED CONSOLIDATED BALANCE SHEETS [Abstract]
Unbilled voyage receivable (in dollars)	$ 47,740	$ 38,430
Voyage receivables, allowance for credit losses	95	55
Vessels and other property, accumulated depreciation	$ 209,090	$ 186,084
Common stock, shares authorized	100,000,000	100,000,000
Common stock, no par value	$ 0	$ 0
Common stock, shares, issued	28,128,298	28,014,877
Common stock, shares, outstanding	28,128,298	28,014,877

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Shipping Revenues:
Shipping revenues	$ 46,304	$ 139,725	$ 93,060	$ 265,062
Operating Expenses:
Voyage expenses	1,586	4,436	3,173	10,042
Vessel expenses	27,877	30,278	54,204	63,238
Charter hire expenses	5,863	7,540	11,604	17,771
Depreciation and amortization	17,079	18,880	33,833	37,147
General and administrative	6,829	6,694	14,969	14,128
Provision for credit losses, net	2	(129)	43	(67)
Third-party debt modification fees	0	0	0	232
Merger and integration related costs	481		481	0
Loss on disposal of vessels and other property, including impairments	4,005	4,134	4,016	1,330
Total operating expenses	63,722	71,833	122,323	143,821
(Loss)/income from vessel operations	(17,418)	67,892	(29,263)	121,241
Equity in income of affiliated companies	5,375	5,205	10,843	10,316
Operating (loss)/income	(12,043)	73,097	(18,420)	131,557
Other income/(expense)	267	143	559	(13,289)
(Loss)/income before interest expense and income taxes	(11,776)	73,240	(17,861)	118,268
Interest expense	(7,006)	(8,881)	(14,286)	(20,890)
(Loss)/income before income taxes	(18,782)	64,359	(32,147)	97,378
Income tax provision	(1)	(1)	(1)	(1)
Net (loss)/income	$ (18,783)	$ 64,358	$ (32,148)	$ 97,377
Weighted Average Number of Common Shares Outstanding:
Basic	28,051,946	28,469,969	28,037,957	28,812,299
Diluted	28,051,946	28,639,780	28,037,957	28,989,146
Per Share Amounts:
Basic net (loss)/income per share	$ (0.67)	$ 2.26	$ (1.15)	$ 3.37
Diluted net (loss)/income per share	$ (0.67)	$ 2.24	$ (1.15)	$ 3.35
Pool Revenue Leases [Member]
Shipping Revenues:
Shipping revenues	$ 26,455	$ 100,059	$ 51,114	$ 201,268
Time and Bareboat Charter Leases [Member]
Shipping Revenues:
Shipping revenues	11,714	26,655	26,412	35,259
Voyage Charter Leases [Member]
Shipping Revenues:
Shipping revenues	$ 8,135	$ 13,011	$ 15,534	$ 28,535

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Pool revenues, received from companies accounted for by the equity method	$ 17,857	$ 71,282	$ 35,104	$ 141,957

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) [Abstract]
Net (loss)/income	$ (18,783)	$ 64,358	$ (32,148)	$ 97,377
Other comprehensive (loss)/income, net of tax:
Net change in unrealized losses on cash flow hedges	(461)	(1,183)	9,822	(16,168)
Defined benefit pension and other postretirement benefit plans:
Net change in unrecognized prior service costs	(7)	8	(15)	80
Net change in unrecognized actuarial losses	(55)	56	(111)	577
Other comprehensive (loss)/income, net of tax	(523)	(1,119)	9,696	(15,511)
Comprehensive (loss)/income	$ (19,306)	$ 63,239	$ (22,452)	$ 81,866

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash Flows from Operating Activities:
Net (loss)/income	$ (32,148)	$ 97,377
Items included in net (loss)/income not affecting cash flows:
Depreciation and amortization	33,833	37,147
Loss on write-down of vessels and other assets	3,497	5,469
Amortization of debt discount and other deferred financing costs	1,077	1,708
Deferred financing costs write-off	0	12,501
Stock compensation	2,263	2,503
Earnings of affiliated companies	(10,843)	(10,209)
Change in fair value of interest rate collar recorded through earnings	0	1,271
Write-off of registration statement costs	694	0
Other - net	831	512
Items included in net (loss)/income related to investing and financing activities:
Loss/(gain) on disposal of vessels and other property, net	519	(4,139)
Loss on extinguishment of debt	0	1,014
Cash distributions from affiliated companies	3,625	5,250
Payments for drydocking	(14,720)	(12,513)
Insurance claims proceeds related to vessel operations	710	570
Changes in operating assets and liabilities:
Increase in receivables	(7,619)	(17,031)
Decrease in deferred revenue	(2,995)	2,970
Net change in inventories, prepaid expenses and other current assets and accounts payable, accrued expenses, and other current and long-term liabilities	(1,242)	3,290
Net cash (used in)/provided by operating activities	(22,518)	127,690
Cash Flows from Investing Activities:
Expenditures for vessels and vessel improvements	(24,130)	(40,949)
Proceeds from disposal of vessels and other property, net	3,431	13,578
Expenditures for other property	(271)	(348)
Investments in and advances to affiliated companies, net	(95)	(46)
Net cash used in investing activities	(21,065)	(27,765)
Cash Flows from Financing Activities:
Issuance of debt, net of issuance costs	(49)	362,989
Extinguishment of debt	0	(382,699)
Payments on debt	(30,742)	(51,266)
Cash payments on derivatives containing other-than-insignificant financing element	(2,623)	0
Common stock issuance costs	(717)	(122)
Cash dividends paid	(3,369)	(3,412)
Repurchases of common stock	0	(29,997)
Cash paid to tax authority upon vesting of stock-based compensation	(1,030)	(1,200)
Net cash used in financing activities	(38,530)	(105,707)
Net decrease in cash, cash equivalents and restricted cash	(82,113)	(5,782)
Cash, cash equivalents and restricted cash at beginning of year	215,677	150,243
Cash, cash equivalents and restricted cash at end of period	$ 133,564	$ 144,461

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Common Stock [Member]Restricted Stock [Member]	Common Stock [Member]Restricted Stock Units (RSUs) [Member]	Common Stock [Member]	Retained Earnings / (Accumulated deficit) [Member]Restricted Stock [Member]	Retained Earnings / (Accumulated deficit) [Member]Restricted Stock Units (RSUs) [Member]	Retained Earnings / (Accumulated deficit) [Member]	Accumulated Other Comprehensive Loss [Member]Restricted Stock [Member]	Accumulated Other Comprehensive Loss [Member]Restricted Stock Units (RSUs) [Member]	Accumulated Other Comprehensive Loss [Member]	Restricted Stock [Member]	Restricted Stock Units (RSUs) [Member]	Total
Balance, beginning at Dec. 31, 2019			$ 1,313,178			$ (270,315)			$ (20,570)			$ 1,022,293
Net (loss)/income			0			97,377			0			97,377
Other comprehensive income/(loss)			0			0			(15,511)			(15,511)
Common stock cash dividends			(3,412)			0			0			(3,412)
Forfeitures of vested restricted stock awards			(1,200)			0			0			(1,200)
Compensation relating to restricted stock units or restricted stock awards	$ 406	$ 1,589		$ 0	$ 0		$ 0	$ 0		$ 406	$ 1,589
Compensation relating to stock option awards			508			0			0			508
Repurchase of common stock			(29,997)			0			0			(29,997)
Balance, ending at Jun. 30, 2020			1,281,072			(172,938)			(36,081)			1,072,053
Balance, beginning at Mar. 31, 2020			1,301,938			(237,296)			(34,962)			1,029,680
Net (loss)/income			0			64,358			0			64,358
Other comprehensive income/(loss)			0			0			(1,119)			(1,119)
Common stock cash dividends			(1,683)			0			0			(1,683)
Forfeitures of vested restricted stock awards			(495)			0			0			(495)
Compensation relating to restricted stock units or restricted stock awards	177	834		0	0		0	0		177	834
Compensation relating to stock option awards			286			0			0			286
Repurchase of common stock			(19,985)			0			0			(19,985)
Balance, ending at Jun. 30, 2020			1,281,072			(172,938)			(36,081)			1,072,053
Balance, beginning at Dec. 31, 2020			1,280,501			(275,846)			(32,613)			972,042
Net (loss)/income			0			(32,148)			0			(32,148)
Other comprehensive income/(loss)			0			0			9,696			9,696
Common stock cash dividends			(3,369)			0			0			(3,369)
Forfeitures of vested restricted stock awards			(1,030)			0			0			(1,030)
Compensation relating to restricted stock units or restricted stock awards	460	1,192		0	0		0	0		460	1,192
Compensation relating to stock option awards			611			0			0			611
Balance, ending at Jun. 30, 2021			1,278,365			(307,994)			(22,917)			947,454
Balance, beginning at Mar. 31, 2021			1,279,368			(289,211)			(22,394)			967,763
Net (loss)/income			0			(18,783)			0			(18,783)
Other comprehensive income/(loss)			0			0			(523)			(523)
Common stock cash dividends			(1,688)			0			0			(1,688)
Forfeitures of vested restricted stock awards			(541)			0			0			(541)
Compensation relating to restricted stock units or restricted stock awards	$ 258	$ 650		$ 0	$ 0		$ 0	$ 0		$ 258	$ 650
Compensation relating to stock option awards			318			0			0			318
Balance, ending at Jun. 30, 2021			$ 1,278,365			$ (307,994)			$ (22,917)			$ 947,454

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2021
BASIS OF PRESENTATION [Abstract]
BASIS OF PRESENTATION	Note 1 — Basis of Presentation: ​ The accompanying unaudited condensed consolidated financial statements include the accounts of International Seaways, Inc. (“INSW”), a Marshall Islands corporation, and its wholly owned subsidiaries. As of June 30, 2021, the Company owned and operated a fleet of 36 oceangoing vessels, including three vessels that have been chartered-in under operating leases for durations exceeding one year at inception and two vessels in which the Company has interests through its joint ventures, engaged primarily in the transportation of crude oil and refined petroleum products in the International Flag trade through its wholly owned subsidiaries. In addition to its operating fleet of 36 vessels, three dual-fuel LNG VLCC newbuilds are scheduled for delivery to the Company in the first quarter of 2023, bringing the total operating and newbuild fleet to 39 vessels as of June 30, 2021. Subsequent to June 30, 2021, the Company’s operating and newbuild fleet increased to 97 vessels upon the completion of the Company’s acquisition of 64 vessels through the merger transaction described below in Note 2, “Merger Transaction,” the sales of a The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. They do not include all of the information and notes required by generally accepted accounting principles in the United States. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the results have been included. Operating results for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. ​ The condensed consolidated balance sheet as of December 31, 2020 has been derived from the audited financial statements at that date but does not include all of the information and notes required by generally accepted accounting principles in the United States for complete financial statements. For further information, refer to the consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. ​ All intercompany balances and transactions within INSW have been eliminated. Investments in 50% or less owned affiliated companies, in which INSW exercises significant influence, are accounted for by the equity method.

MERGER TRANSACTIONS

MERGER TRANSACTIONS	6 Months Ended
	Jun. 30, 2021
Merger Transactions [Abstract}
Merger Transaction	Note 2 — Merger Transaction: ​ Completion of Merger Transaction ​ On July 16, 2021 (the “Effective Time”), pursuant to an Agreement and Plan of Merger (the “Merger Agreement”) dated as of March 30, 2021, by and among INSW, Diamond S Shipping Inc., a Republic of the Marshall Islands corporation (“Diamond S”), and Dispatch Transaction Sub, Inc., a Republic of the Marshall Islands corporation and wholly-owned subsidiary of INSW (“Merger Sub”), Merger Sub merged with and into Diamond S (the “Merger”), with Diamond S surviving such merger as a wholly owned subsidiary of INSW. Immediately following the Effective Time, the Company contributed all of the outstanding stock of Diamond S to International Seaways Operating Corporation, a direct wholly-owned subsidiary of the Company. ​ At the Effective Time, each common share of Diamond S (the “Diamond S Common Shares”) issued and outstanding immediately prior to the Effective Time (excluding Diamond S Common Shares owned by Diamond S, the Company, Merger Sub or any of their respective direct or indirect wholly-owned subsidiaries) was cancelled in exchange for the right to receive 0.55375 of a share of common stock of the Company (the “ INSW Common Stock ”) and cash payable in respect of fractional shares. The aforementioned 0.55375 exchange ratio set forth in the Merger Agreement resulted in the issuance of 22,536,647 shares of INSW Common Stock, with the pre-merger INSW shareholders and the former Diamond S shareholders owning approximately 55.75% and 44.25% , respectively, of the 50,674,393 issued and outstanding common stock of the Company immediately following the Effective Time. ​ As provided for under the terms of the Merger Agreement, on July 15, 2021, prior to the Effective Time, INSW paid a special dividend to its shareholders of record as of July 14, 2021 in an aggregate amount equal to $31.5 million ( $1.12 per share). ​ Amended and Restated Debt Agreements ​ In connection with the Merger, lenders under Diamond S’ existing credit facilities agreed, among other things, to consent to the Merger and waive any event of default that would arise as a result of the Merger. On May 27, 2021, the Company entered into Amendment and Restatement Agreements with (i) Diamond S, Nordea Bank Abp, New York Branch, as Administrative Agent, and the lenders constituting the Required Lenders under that certain credit agreement of Diamond S first dated as of March 27, 2019 (the “ $360 Million Credit Agreement”) in order to amend and restate Diamond S’ $360 Million Credit Agreement (as amended and restated, the “Amended and Restated $360 Million Credit Agreement”) and (ii) Diamond S, Nordea Bank Abp, New York Branch, as Administrative Agent, and the lenders constituting the Required Lenders under that certain credit agreement of Diamond S, first dated as of December 23, 2019 (the “ $525 Million Credit Agreement”), in order to amend and restate Diamond S’ $525 Million Credit Agreement (as amended and restated, the “Amended and Restated $525 Million Credit Agreement” and together with the Amended and Restated $360 Million Credit Agreement, the “Amendment and Restatement Agreements”). On May 27, 2021, the Company executed a guarantee of Diamond S’ obligations under each of the Amended and Restated $360 Million Credit Agreement and the Amended and Restated $525 Million Credit Agreement (the “INSW Guarantees”). ​ At the Effective Time, as a result of the consummation of the Merger, and following the payment by Diamond S of fees required to be paid to the lenders, the Amendment and Restatement Agreements and INSW Guarantees became effective. Directors and Certain Officers ​ Pursuant to the Merger Agreement, following the Effective Time, the Company now has a board of directors (the “Board”) consisting of ten directors comprised of (i) a chairman, designated by the Company, (ii) six additional directors, designated by the Company and (iii) three additional directors, designated by Diamond S. ​ Effective as of the Effective Time, as contemplated by the Merger Agreement to permit three directors designated by Diamond S to serve on the Board, Mr. Ty E. Wallach resigned as a member of the Board. Mr. Wallach was a member of the Human Resources and Compensation committee of the Board. In connection with his resignation from the Board, the Board approved the accelerated vesting of his 5,035 shares of restricted INSW Common Stock. ​ The three vacancies created by the resignation of Mr. Wallach and the expansion of the Board were filled by the Board with Mr. Craig H. Stevenson Jr., Alexandra K. Blankenship and Nadim Qureshi, the three directors designated by Diamond S in accordance with the Merger Agreement. Each of Mr. Stevenson, Ms. Blankenship and Mr. Qureshi was a director of Diamond S immediately prior to the Effective Time and will serve as a member of the Board until the Company’s 2022 annual meeting of stockholders or until his or her earlier death, resignation or removal. Ms. Blankenship will also serve as a member of the Audit Committee of the Board and Mr. Qureshi will fill the vacancy on the Human Resources and Compensation Committee of the Board. Each of Mr. Stevenson, Ms. Blankenship and Mr. Qureshi will be compensated in accordance with the director compensation program as described in the Company’s definitive Proxy Statement filed with the SEC on May 5, 2021 (reduced on an appropriate pro rata basis with respect to service in 2021). In connection with joining the Board, it is expected that Mr. Stevenson, Ms. Blankenship and Mr. Qureshi will enter into customary indemnification agreements with the Company. On July 14, 2021, in connection with the consummation of the Merger, the Company entered into a letter agreement with Mr. Stevenson, Jr. (the “Letter Agreement”). The Letter Agreement provides that during the period from July 14, 2021, until the earlier of six months following such date and the date of termination of such engagement, in addition to serving as a director, Mr. Stevenson will provide services to the Company as special advisor to the Chief Executive Officer of the Company. During the advisory period, Mr. Stevenson will receive a total consulting fee equal to $0.5 million, paid in equal monthly installments, subject to reduction in the case of certain termination of services events prior to the expiration of such six-month period. ​ Following the Merger, the senior management of INSW remain in their current roles and lead the Company. ​ Accounting for the Merger ​ Based on the terms of the Merger Agreement, the Merger was determined to not meet the requirements of a business combination under the guidelines of ASC 805, Business Combinations Business Combinations ​ As of June 30, 2021,

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Note 3 — Significant Accounting Policies: ​ For a description of all of the Company’s material accounting policies, see Note 2, “Summary of Significant Accounting Policies,” to the Company’s consolidated financial statements as of and for the year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K. The following is a summary of any changes or updates to the Company’s critical accounting policies for the current period: ​ Cash, cash equivalents and restricted cash — ​ Concentration of Credit Risk — ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Allowance for Credit Losses - Balance at December 31, 2020 ​ $ 55 Provision for expected credit losses ​ ​ 43 Write-offs charged against the allowance ​ ​ (3) Balance at June 30, 2021 ​ $ 95 ​ We are also exposed to credit losses from off-balance sheet exposures related to guarantees of joint venture debt. See Note 7, “Equity Method Investments,” for more information on these off-balance sheet exposures. ​ During the three and six months ended June 30, 2021 and 2020, the Company did not have any individual customers who accounted for 10% or more of its revenues apart from the pools in which it participates. The pools in which the Company participates accounted in aggregate for 94% and 88% of consolidated voyage receivables at June 30, 2021 and December 31, 2020, respectively. ​ Deferred finance charges — Revolving Facility (See Note 10, “Debt”) as of June 30, 2021 and December 31, 2020, respectively, are included in other assets in the condensed consolidated balance sheets. Unamortized deferred financing charges of $5.9 million and $6.9 million relating to the Company’s outstanding debt facilities as of June 30, 2021 and December 31, 2020, respectively, are included in long-term debt in the condensed consolidated balance sheets. Interest expense relating to the amortization of deferred financing charges amounted to $0.5 million and $1.0 million for the three and six months ended June 30, 2021, respectively, and $0.7 million and $1.6 million for the three and six months ended June 30, 2020, respectively. ​ Vessels — ​ Recently Issued Accounting Standards Reference Rate Reform which provides relief for companies preparing for discontinuation of interest rates such as LIBOR. A contract modification is eligible to apply the optional relief to account for the modifications as a continuation of the existing contracts without additional analysis and consider embedded features to be clearly and closely related to the host contract without reassessment, if all of the following criteria are met: (1) contract references a rate that will be discontinued; (2) modified terms directly replace (or have potential to replace) this reference rate; and (3) changes to any other terms that change (or have potential to change) amount and timing of cash flows must be related to replacement of the reference rate. In addition, this guidance provides relief from certain hedge accounting requirements. Hedge accounting may continue uninterrupted when critical terms change due to reference rate reform. For cash flow hedges, entities can (1) disregard potential discontinuation of a referenced interest rate when assessing whether a hedged forecasted interest payment is probable; (2) continue hedge accounting upon a change in the hedged risk as long as the hedge is still highly effective; (3) assess effectiveness of the hedge relationship in ways that essentially disregards a potential mismatch in the variable rate indices between the hedging instrument and the hedged item; and (4) disregard the requirement that individual hedged transactions must share the same risk exposure for hedges of portfolios of forecasted transactions that reference a rate affected by reference rate reform. Relief provided by this ASU is optional and expires December 31, 2022. In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (ASC 848) to refine the scope of ASC 848 and to clarify some of its guidance. The Company has determined that its primary exposure to LIBOR is in relation to its floating rate debt facilities and the interest rate derivatives to which it is a party. On November 30, 2020, the benchmark administrator for the U.S. Dollar (“USD”) LIBOR announced a proposal to extend the publication of the most commonly used USD LIBOR settings until June 30, 2023. In light of this proposal, in an interagency statement, the Board of Governors of the Federal Reserve System, the Federal Deposit Insurance Corporation, and the Office of the Comptroller of the Currency issued guidance, strongly encouraging banks to cease entering into new contracts that use USD LIBOR as a reference rate as soon as practicable and in any event by December 31, 2021. Only in limited circumstances will it be appropriate for banks to enter into new contracts referencing USD LIBOR after December 31, 2021. The principal objective, and result, of these actions appears to be that legacy USD LIBOR-based instruments (i.e., those maturing after December 31, 2021) may continue to use USD LIBOR as a reference rate through June 30, 2023, without undermining the regulators’ determination that LIBOR should not be available for any other purpose. On January 25, 2021, the International Swaps and Derivatives Association, Inc. (“ISDA”), published new fallback provisions for derivatives linked to key interbank offered rates (“IBOR”) which will be incorporated into all new derivatives contracts that reference ISDA’s standard interest rate derivatives definitions. Such fallback provisions will also be included in legacy non-cleared derivatives if the counterparties have bilaterally agreed to include them or both have adhered to the IBOR fallback protocol. The Company has engaged and will continue to engage in discussions with its lending banks and the counterparties to its interest rate derivative contracts in advance of the June 30, 2023 sunset date for the USD LIBOR reference rate settings used in its agreements to evaluate the Company’s options. Based on information available today, the Company’s current view is that the Secured Overnight Financing Rate (“SOFR”) will be the alternative reference rate that the Company’s LIBOR-based agreements will transition to as the sunset date draws closer.

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	6 Months Ended
	Jun. 30, 2021
EARNINGS PER COMMON SHARE [Abstract]
EARNINGS PER COMMON SHARE	Note 4 — Earnings per Common Share: ​ Basic earnings per common share is computed by dividing earnings, after the deduction of dividends and undistributed earnings allocated to participating securities, by the weighted average number of common shares outstanding during the period. ​ The computation of diluted earnings per share assumes the issuance of common stock for all potentially dilutive stock options and restricted stock units not classified as participating securities. Participating securities are defined by ASC 260, Earnings Per Share unvested share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents and are included in the computation of earnings per share pursuant to the two-class method. ​ Weighted average shares of unvested restricted common stock considered to be participating securities totaled 61,437 and 56,291 for the three and six months ended June 30, 2021, respectively, and 39,093 and 45,100 for the three and six months ended June 30, 2020, respectively. Such participating securities are allocated a portion of income, but not losses under the two-class method. As of June 30, 2021, there were 272,922 shares of restricted stock units and 811,906 stock options outstanding and considered to be potentially dilutive securities. ​ Reconciliations of the numerator of the basic and diluted earnings per share computations are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Net (loss)/income allocated to: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common Stockholders ​ $ (18,785) ​ $ 64,272 ​ $ (32,154) ​ $ 97,227 Participating securities ​ ​ 2 ​ ​ 86 ​ ​ 6 ​ ​ 150 ​ ​ $ (18,783) ​ $ 64,358 ​ $ (32,148) ​ $ 97,377 ​ For the three and six months ended June 30, 2021 earnings per share calculations, there were no dilutive equity awards outstanding. For the three and six months ended June 30, 2020 earnings per share calculations, there were 169,811 and 176,847 dilutive equity awards outstanding, respectively. Awards of 1,086,589 and 1,013,234 for the three and six months ended June 30, 2021, respectively, and 965,994 and 891,853 for the three and six months ended June 30, 2020, respectively, were not included in the computation of diluted earnings per share because inclusion of these awards would be anti-dilutive.

BUSINESS AND SEGMENT REPORTING

BUSINESS AND SEGMENT REPORTING	6 Months Ended
	Jun. 30, 2021
BUSINESS AND SEGMENT REPORTING [Abstract]
BUSINESS AND SEGMENT REPORTING	Note 5 — Business and Segment Reporting: ​ The Company has two reportable segments: Crude Tankers and Product Carriers. The Company’s investments in and equity in income of the joint ventures with two floating storage and offloading service vessels are included in the Crude Tankers Segment. Adjusted income/(loss) from vessel operations for segment purposes is defined as income/(loss) from vessel operations before general and administrative expenses, provision for credit losses, third-party debt modification fees, merger and integration related costs and loss on disposal of vessels and other property, including impairments. The accounting policies followed by the reportable segments are the same as those followed in the preparation of the Company’s condensed consolidated financial statements. ​ ​ Information about the Company’s reportable segments as of and for the three and six months ended June 30, 2021 and 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Other ​ Totals Three months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 32,548 ​ $ 13,756 ​ $ — ​ $ 46,304 Time charter equivalent revenues ​ ​ 31,096 ​ ​ 13,622 ​ ​ — ​ ​ 44,718 Depreciation and amortization ​ ​ 13,039 ​ ​ 4,022 ​ ​ 18 ​ ​ 17,079 Loss on disposal of vessels and other property, including impairments ​ ​ 4,005 ​ ​ — ​ ​ — ​ ​ 4,005 Adjusted (loss)/income from vessel operations ​ ​ (7,058) ​ ​ 975 ​ ​ (18) ​ ​ (6,101) Equity in income of affiliated companies ​ ​ 5,375 ​ ​ — ​ ​ — ​ ​ 5,375 Investments in and advances to affiliated companies at June 30, 2021 ​ ​ 142,171 ​ ​ 7,409 ​ ​ — ​ ​ 149,580 Adjusted total assets at June 30, 2021 ​ ​ 1,122,807 ​ ​ 251,310 ​ ​ — ​ ​ 1,374,117 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 110,407 ​ $ 29,318 ​ $ — ​ $ 139,725 Time charter equivalent revenues ​ ​ 105,890 ​ ​ 29,399 ​ ​ — ​ ​ 135,289 Depreciation and amortization ​ ​ 14,732 ​ ​ 4,125 ​ ​ 23 ​ ​ 18,880 Loss on disposal of vessels and other property, including impairments ​ ​ 4,134 ​ ​ — ​ ​ — ​ ​ 4,134 Adjusted income/(loss) from vessel operations ​ ​ 62,883 ​ ​ 15,731 ​ ​ (23) ​ ​ 78,591 Equity in income of affiliated companies ​ ​ 5,205 ​ ​ — ​ ​ — ​ ​ 5,205 Investments in and advances to affiliated companies at June 30, 2020 ​ ​ 146,861 ​ ​ 8,330 ​ ​ — ​ ​ 155,191 Adjusted total assets at June 30, 2020 ​ ​ 1,288,235 ​ ​ 321,530 ​ ​ — ​ ​ 1,609,765 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Other ​ Totals Six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 70,058 ​ $ 23,002 ​ $ — ​ $ 93,060 Time charter equivalent revenues ​ ​ 67,046 ​ ​ 22,841 ​ ​ — ​ ​ 89,887 Depreciation and amortization ​ ​ 26,042 ​ ​ 7,750 ​ ​ 41 ​ ​ 33,833 Loss on disposal of vessels and other property, including impairments ​ ​ 4,016 ​ ​ — ​ ​ — ​ ​ 4,016 Adjusted loss from vessel operations ​ ​ (8,015) ​ ​ (1,698) ​ ​ (41) ​ ​ (9,754) Equity in income of affiliated companies ​ ​ 10,843 ​ ​ — ​ ​ — ​ ​ 10,843 Expenditures for vessels and vessel improvements ​ ​ 22,359 ​ ​ 1,771 ​ ​ — ​ ​ 24,130 Payments for drydocking ​ ​ 7,992 ​ ​ 6,728 ​ ​ — ​ ​ 14,720 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 204,084 ​ $ 60,978 ​ $ — ​ $ 265,062 Time charter equivalent revenues ​ ​ 194,744 ​ ​ 60,276 ​ ​ — ​ ​ 255,020 Depreciation and amortization ​ ​ 28,977 ​ ​ 8,123 ​ ​ 47 ​ ​ 37,147 Loss on disposal of vessels and other property, including impairments ​ ​ 1,330 ​ ​ — ​ ​ — ​ ​ 1,330 Adjusted income/(loss) from vessel operations ​ ​ 106,824 ​ ​ 30,087 ​ ​ (47) ​ ​ 136,864 Equity in income of affiliated companies ​ ​ 10,316 ​ ​ — ​ ​ — ​ ​ 10,316 Expenditures for vessels and vessel improvements ​ ​ 22,451 ​ ​ 18,498 ​ ​ — ​ ​ 40,949 Payments for drydockings ​ ​ 12,121 ​ ​ 392 ​ ​ — ​ ​ 12,513 ​ ​ Reconciliations of time charter equivalent (“TCE”) revenues of the segments to shipping revenues as reported in the condensed statements of operations follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Time charter equivalent revenues ​ $ 44,718 ​ $ 135,289 ​ $ 89,887 ​ $ 255,020 Add: Voyage expenses ​ ​ 1,586 ​ ​ 4,436 ​ ​ 3,173 ​ ​ 10,042 Shipping revenues ​ $ 46,304 ​ $ 139,725 ​ $ 93,060 ​ $ 265,062 ​ Consistent with general practice in the shipping industry, the Company uses time charter equivalent revenues, which represent shipping revenues less voyage expenses, as a measure to compare revenue generated from a voyage charter to revenue generated from a time charter. Time charter equivalent revenues, a non-GAAP measure, provide additional meaningful information in conjunction with shipping revenues, the most directly comparable GAAP measure, because it assists Company management in making decisions regarding the deployment and use of its vessels and in evaluating their financial performance. ​ Reconciliations of adjusted (loss)/income from vessel operations of the segments to (loss)/income before income taxes, as reported in the condensed consolidated statements of operations follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Total adjusted (loss)/income from vessel operations of all segments ​ $ (6,101) ​ $ 78,591 ​ $ (9,754) ​ $ 136,864 General and administrative expenses ​ ​ (6,829) ​ ​ (6,694) ​ ​ (14,969) ​ ​ (14,128) Provision for credit losses, net ​ ​ (2) ​ ​ 129 ​ ​ (43) ​ ​ 67 Third-party debt modification fees ​ ​ — ​ ​ — ​ ​ — ​ ​ (232) Merger and integration related costs ​ ​ (481) ​ ​ — ​ ​ (481) ​ ​ — Loss on disposal of vessels and other property, including impairments ​ ​ (4,005) ​ ​ (4,134) ​ ​ (4,016) ​ ​ (1,330) Consolidated (loss)/income from vessel operations ​ ​ (17,418) ​ ​ 67,892 ​ ​ (29,263) ​ ​ 121,241 Equity in income of affiliated companies ​ ​ 5,375 ​ ​ 5,205 ​ ​ 10,843 ​ ​ 10,316 Other income/(expense) ​ ​ 267 ​ ​ 143 ​ ​ 559 ​ ​ (13,289) Interest expense ​ ​ (7,006) ​ ​ (8,881) ​ ​ (14,286) ​ ​ (20,890) (Loss)/income before income taxes ​ $ (18,782) ​ $ 64,359 ​ $ (32,147) ​ $ 97,378 ​ Reconciliations of total assets of the segments to amounts included in the condensed consolidated balance sheets follow: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 ​ June 30, 2020 Adjusted total assets of all segments ​ $ 1,374,117 ​ $ 1,609,765 Corporate unrestricted cash and cash equivalents ​ ​ 117,391 ​ ​ 128,063 Restricted cash ​ ​ 16,173 ​ ​ 16,398 Other unallocated amounts ​ ​ 11,184 ​ ​ 4,730 Consolidated total assets ​ $ 1,518,865 ​ $ 1,758,956 ​

VESSELS

VESSELS	6 Months Ended
	Jun. 30, 2021
VESSELS [Abstract]
VESSELS	Note 6 — Vessels: ​ Vessel Impairments ​ The Company gave consideration as to whether events or changes in circumstances had occurred since December 31, 2020 that could indicate that the carrying amounts of the vessels in the Company’s fleet may not be recoverable as of June 30, 2021 and concluded that the contracted sale of one 2003-built Panamax resulted in a held-for-sale impairment as of June 30, 2021. Held-for-sale impairment charges aggregating $3.5 million were recorded during the second quarter of 2021 including a charge of $3.4 million to write the value of the held-for-sale Panamax down to its estimated fair value at June 30, 2021, and a charge of $0.1 million for estimated costs to sell the vessel. The amount of the charge to write down the vessel to its fair value was determined using the market approach by utilizing the sales price as per the memorandum of agreement associated with the sale of the vessel. ​ Construction Commitments ​ On March 11, 2021, the Company entered into agreements to construct three dual-fuel LNG VLCCs at Daewoo Shipbuilding and Marine Engineering’s shipyard. Title and risk of the vessels remain with the shipyard while the vessels are under construction until delivered to the Company. The VLCCs will be able to burn LNG in their power plant, which will significantly reduce greenhouse gas emissions. Upon delivery to the Company in the first quarter of 2023, the vessels will be employed on seven-year time charter contracts with an oil major – Shell. The total construction cost for the vessels will be approximately $290.0 million, which will be paid for through a combination of long-term financing, cash on hand and availability under the Company’s Core Revolving Facility. essels construction in progress as of June 30, 2021. Remaining commitments on the contracts for the construction of these vessels as of June 30, 2021 was $273.8 million. ​ Vessel sales ​ During the first half of 2021, the Company entered into memoranda of agreements for the sale of a 2002-built VLCC, a 2002-built Panamax and the aforementioned 2003-built Panamax. The 2002-built VLCC and the 2003-built Panamax, are classified as vessels held for sale in the accompanying condensed consolidated balance sheet as of June 30, 2021. The 2002-built VLCC was delivered to its buyers in July 2021 and the two Panamaxes are expected to be delivered to their buyers sometime in August 2021. The Company received deposits totaling $3.9 million related to the two Panamaxes, which are included in cash and cash equivalents in the accompanying condensed consolidated balance sheet as of June 30, 2021. ​ On June 30, 2021, the Company entered into memoranda of agreements for the sale of six MRs acquired as part of the Merger (see Note 2, “Merger Transaction”). Such agreements were subject to the successful closing of the Merger, which occurred on July 16, 2021. The six MRs, which were built between 2006 and 2008, are expected to be delivered to their buyer during the third quarter of 2021. ​ On July 21, 2021, the Company entered into a memorandum of agreement for the sale of a ​ On July 28, 2021, the Company entered into memoranda of agreements for the sale of two additional 2002-built Panamaxes, which are expected to be delivered to their buyers between the end of the third quarter of 2021 and early in the fourth quarter of 2021. ​

EQUITY METHOD INVESTMENTS

EQUITY METHOD INVESTMENTS	6 Months Ended
	Jun. 30, 2021
EQUITY METHOD INVESTMENTS [Abstract]
EQUITY METHOD INVESTMENTS	Note 7 — Equity Method Investments: ​ Investments in affiliated companies include joint ventures accounted for using the equity method. As of June 30, 2021, the Company had a 50% interest in two joint ventures - TI Africa Limited (“TI Africa”) and TI Asia Limited (“TI Asia”), which operate two Floating Storage and Offloading Service vessels that were converted from two ULCCs (collectively the “FSO Joint Venture”). ​ The FSO Joint Venture is a party to a number of contracts: (a) the FSO Joint Venture is an obligor pursuant to a guarantee facility agreement dated as of July 14, 2017, by and among, the FSO Joint Venture, ING Belgium NV/SA, as issuing bank, and Euronav and INSW, as guarantors (the “Guarantee Facility”); (b) the FSO Joint Venture is party to two service contracts with NOC (the “NOC Service Contracts”) and (c) the FSO Joint Venture is a borrower under a $220 million secured credit facility by and among TI Africa and TI Asia, as joint and several borrowers, ABN AMRO Bank N.V. and ING Belgium SA/NV, as Lenders, Mandated Lead Arrangers and Swap Banks, and ING Bank N.V., as Agent and as Security Trustee. INSW severally guarantees the obligations of the FSO Joint Venture pursuant to the Guarantee Facility. ​ The FSO Joint Venture drew down on a $220 million credit facility in April 2018. The Company provided a guarantee for the $110 million FSO Term Loan portion of the facility, which has an interest rate of LIBOR plus two percent and not be less than the higher of $50 million and 5% of Total Indebtedness of INSW, (ii) INSW shall have Cash of at least $30 million and (iii) INSW shall be in compliance with the Loan to Value Test (as such capitalized terms are defined in the Company guarantee). As of June 30, 2021, the maximum aggregate potential amount of future payments (undiscounted) that INSW could be required to make in relation to its equity method investees secured bank debt and interest rate swap obligations was $33.2 million and the carrying value of the Company’s guaranty in the accompanying condensed consolidated balance sheet was $3 thousand. ​ Investments in and advances to affiliated companies as reflected in the accompanying condensed consolidated balance sheet as of June 30, 2021 consisted of: FSO Joint Venture of $136.5 million and Other of $13.1 million, which primarily relates to working capital deposits that the Company maintains for commercial pools in which it participates. ​ A condensed summary of the results of operations of the joint ventures follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Shipping revenues ​ $ 26,109 ​ $ 26,119 ​ $ 51,954 ​ $ 52,143 Ship operating expenses ​ ​ (14,439) ​ ​ (14,241) ​ ​ (28,370) ​ ​ (28,481) Income from vessel operations ​ ​ 11,670 ​ ​ 11,878 ​ ​ 23,584 ​ ​ 23,662 Other (expense)/income ​ ​ (9) ​ ​ — ​ ​ (9) ​ ​ 40 Interest expense ​ ​ (1,098) ​ ​ (1,721) ​ ​ (2,310) ​ ​ (3,595) Income tax provision ​ ​ (981) ​ ​ (944) ​ ​ (1,973) ​ ​ (1,867) Net income ​ $ 9,582 ​ $ 9,213 ​ $ 19,292 ​ $ 18,240 ​

VARIABLE INTEREST ENTITIES (VIE

VARIABLE INTEREST ENTITIES (VIEs)	6 Months Ended
	Jun. 30, 2021
VARIABLE INTEREST ENTITIES (VIEs) [Abstract]
VARIABLE INTEREST ENTITIES (VIEs)	Note 8 — Variable Interest Entities (“VIEs”): ​ As of June 30, 2021, the Company participates in five commercial pools and two joint ventures. One of the pools and the two FSO joint ventures were determined to be VIEs. The Company is not considered a primary beneficiary of either the pool or the joint ventures. ​ The following table presents the carrying amounts of assets and liabilities in the condensed consolidated balance sheet related to the VIEs as of June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ ​ ​ Condensed Investments in Affiliated Companies ​ ​ ​ ​ $ 140,603 ​ In accordance with accounting guidance, the Company evaluated its maximum exposure to loss related to these VIEs by assuming a complete loss of the Company’s investment in these VIEs. The table below compares the Company’s liability in the condensed consolidated balance sheet to the maximum exposure to loss at June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Condensed ​ Maximum Exposure to Other Liabilities ​ $ 3 ​ $ 173,853 ​ In addition, as of June 30, 2021, the Company had approximately $14.9 million of trade receivables from the pool that was determined to be a VIE. These trade receivables, which are included in voyage receivables in the accompanying condensed consolidated balance sheet, have been excluded from the above tables and the calculation of INSW’s maximum exposure to loss. The Company does not record the maximum exposure to loss as a liability because it does not believe that such a loss is probable of occurring as of June 30, 2021.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES	6 Months Ended
	Jun. 30, 2021
FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES	Note 9 — Fair Value of Financial Instruments, Derivatives and Fair Value Disclosures: ​ The estimated fair values of the Company’s financial instruments, other than derivatives that are not measured at fair value on a recurring basis, categorized based upon the fair value hierarchy, are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Fair Value ​ Level 1 ​ Level 2 June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents (1) ​ $ 133,564 ​ $ 133,564 ​ $ — Core Term Loan Facility ​ ​ (252,619) ​ ​ — ​ ​ (252,619) Sinosure Credit Facility ​ ​ (234,337) ​ ​ — ​ ​ (234,337) 8.5% Senior Notes ​ ​ (25,600) ​ ​ (25,600) ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents (1) ​ $ 215,677 ​ $ 215,677 ​ $ — Core Term Loan Facility ​ ​ (271,571) ​ ​ — ​ ​ (271,571) Sinosure Credit Facility ​ ​ (246,127) ​ ​ — ​ ​ (246,127) 8.5% Senior Notes ​ ​ (25,697) ​ ​ (25,697) ​ ​ — (1) Includes non-current restricted cash of $16.2 million and $16.3 million at June 30, 2021 and December 31, 2020, respectively. ​ Derivatives ​ The Company uses interest rate collars and swaps for the management of interest rate risk exposure associated with changes in LIBOR interest rate payments due on its credit facilities. ​ During April 2020, the Company entered into an interest rate swap agreement with a major financial institution covering a notional amount of $25 of the ​ The Company is also party to a floating-to-fixed interest rate swap agreement with a major financial institution covering the balance outstanding under the Sinosure Credit Facility that effectively converts the Company’s interest rate exposure under the Sinosure Credit Facility from a floating rate based on three-month LIBOR to a fixed rate. The interest rate swap agreement, which contains no leverage features, is designated and qualifies as a cash flow hedge. In July 2020, the Company extended the maturity date of the interest rate swap from March 21, 2025 to December 21, 2027 and reduced the fixed three-month LIBOR from 2.76% to 2.35%, effective June 21, 2020. The new interest rate swap agreement does not in its entirety meet the definition of a derivative instrument because of its off market fixed rate at inception and is deemed to be a hybrid instrument with a financing component and an embedded at-the-market derivative. Such embedded derivative is bifurcated and accounted for separately in the same manner as the Company’s other derivatives. The financing component is recorded in current and noncurrent other liabilities on the condensed consolidated balance sheets at amortized cost. Due to an other-than-insignificant financing element on a portion of such hybrid instrument, the cash flows associated with this hybrid instrument are classified as financing activities in the consolidated statement of cash flows. ​ ​ Derivatives are recorded on a net basis by counterparty when a legal right of offset exists. The Company had the following amounts recorded on a gross basis by transaction in the accompanying unaudited condensed consolidated balance sheets related to the Company’s use of derivatives as of June 30, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Long-term derivative ​ Current portion of derivative liabilities ​ Long-term derivative ​ Accounts payable, accrued expenses and other current liabilities ​ Other June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ 6,526 ​ $ (3,950) ​ $ (3,782) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (1) ​ ​ — ​ ​ — ​ ​ — ​ ​ (2,907) ​ ​ (12,628) Total ​ $ 6,526 ​ $ (3,950) ​ $ (3,782) ​ $ (2,907) ​ $ (12,628) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ 2,129 ​ $ (4,121) ​ $ (6,155) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (1) ​ ​ — ​ ​ — ​ ​ — ​ ​ (2,979) ​ ​ (14,051) Total ​ $ 2,129 ​ $ (4,121) ​ $ (6,155) ​ $ (2,979) ​ $ (14,051) (1) Represents the financing element of the hybrid instrument discussed above, which is recorded at amortized cost. ​ The following tables present information with respect to gains and losses on derivative positions reflected in the condensed consolidated statements of operations or in the condensed consolidated statements of comprehensive income. ​ The effect of cash flow hedging relationships recognized in other comprehensive income/(loss) excluding amounts reclassified from accumulated other comprehensive loss, including hedges of equity method investees, for the three and six months ended June 30, 2021 and 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ (2,981) ​ $ (2,828) ​ $ 4,765 ​ $ (18,949) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ ​ (450) ​ ​ — ​ ​ (916) ​ ​ — Total other comprehensive loss ​ $ (3,431) ​ $ (2,828) ​ $ 3,849 ​ $ (18,949) ​ ​ The effect of cash flow hedging relationships on the condensed consolidated statement of operations is presented excluding hedges of equity method investees. The effect of the Company’s cash flow hedging relationships on the condensed consolidated statement of operations for the three and six months ended June 30, 2021 and 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ 1,149 ​ $ 1,417 ​ $ 2,265 ​ $ 2,312 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate collar ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,352 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ ​ 1,560 ​ ​ — ​ ​ 3,153 ​ ​ — Total interest expense ​ $ 2,709 ​ $ 1,417 ​ $ 5,418 ​ $ 3,664 ​ See Note 13, “Accumulated Other Comprehensive Loss,” for disclosures relating to the impact of derivative instruments on accumulated other comprehensive loss. ​ The following table presents the fair values, which are pre-tax, for assets and liabilities measured on a recurring basis (excluding investments in affiliated companies): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ ​ ​ Fair Value ​ Level 2 ​ Assets/(Liabilities) at June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative Assets (interest rate swaps) ​ ​ ​ ​ $ 6,526 ​ $ 6,526 (1) Derivative Liabilities (interest rate swaps) ​ ​ ​ ​ ​ (7,732) ​ ​ (7,732) (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets/(Liabilities) at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative Assets (interest rate swaps) ​ ​ ​ ​ $ 2,129 ​ $ 2,129 (1) Derivative Liabilities (interest rate swaps) ​ ​ ​ ​ ​ (10,276) ​ ​ (10,276) (1) (1) For the interest rate swaps, fair values are derived using valuation models that utilize the income valuation approach. These valuation models take into account contract terms such as maturity, as well as other inputs such as interest rate yield curves and creditworthiness of the counterparty and the Company. ​ ​ The following table summarizes the fair values of assets for which an impairment charge was recognized for the three and six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Fair Value ​ ​ Level 2 ​ ​ Total Impairment Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude Tankers - Vessels held for sale (1)(2) ​ $ 6,542 ​ $ 6,542 ​ $ (3,497) (1) Pre-tax impairment charges of $3.5 million related to one Panamax in the Crude Tanker segment were recorded during the three-month period ended June 30, 2021. The held-for-sale impairment charges aggregating $3.5 million as of June 30, 2021 included a charge of $3.4 million to write the value of the vessel down to its estimated fair value, and estimated costs to sell the vessel of $0.1 million. (2) Fair value measurement of $6.5 million at June 30, 2021 used to determine the impairment for one Panamax was based upon a market approach, which considered the expected sale price of the vessel based on an executed memorandum of agreement for the sale of the vessel as discussed in Note 6, "Vessels." Because sales of vessels occur somewhat infrequently the expected sales prices are considered to be Level 2.

DEBT

DEBT	6 Months Ended
	Jun. 30, 2021
DEBT [Abstract]
DEBT	Note 10 — Debt: ​ Debt consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 December 31, 2020 Core Term Loan Facility, due 2025, net of unamortized deferred finance costs of $3,500 and $4,145 ​ $ 249,119 ​ $ 267,427 Sinosure Credit Facility, due 2027-2028, net of unamortized deferred finance costs of $1,706 and $1,884 ​ ​ 232,631 ​ ​ 244,243 8.5% Senior Notes, due 2023, net of unamortized deferred finance costs of $701 and $855 ​ ​ 24,299 ​ ​ 24,145 ​ ​ ​ 506,049 ​ ​ 535,815 Less current portion ​ ​ (61,483) ​ ​ (61,483) Long-term portion ​ $ 444,566 ​ $ 474,332 ​ Capitalized terms used hereafter have the meaning given in these condensed consolidated financial statements or in the respective transaction documents referred to below, including subsequent amendments thereto. ​ Debt Covenants ​ The Company was in compliance with the financial and non-financial covenants under all of its debt facilities as of June 30, 2021. ​ The 2020 Debt Facilities contain customary representations, warranties, restrictions and covenants applicable to the Company, the Borrower and the subsidiary guarantors (and in certain cases, other subsidiaries), including financial covenants that require the Company (i) to maintain a minimum liquidity level of the greater of $50 million and 5% of the Company’s Consolidated Indebtedness; (ii) to ensure the Company’s and its consolidated subsidiaries’ Maximum Leverage Ratio will not exceed 0.60 to 1.00 at any time; (iii) to ensure that Current Assets exceeds Current Liabilities (which is defined to exclude the current potion of Consolidated Indebtedness); (iv) to ensure the aggregate Fair Market Value of the Core Collateral Vessels will not be less than 135% of the aggregate outstanding principal amount of the Core Term Loans and Revolving Loans; and (v) to ensure the ratio of Consolidated EBITDA to Consolidated Cash Interest Expense will not be lower than 2.50:1.00. ​ Under the Sinosure Credit Facility, the Obligors (as defined in the Sinosure Credit Facility) are required to comply with various collateral maintenance and financial covenants, including with respect to: ​ (i) minimum security coverage, which shall not be less than 135% of the aggregate loan principal outstanding under the Sinosure Credit Facility. Any non-compliance with the minimum security coverage shall not constitute an event of default so long as within thirty days of such non-compliance, Seaways Subsidiary VII, Inc. has either provided additional collateral or prepaid a portion of the outstanding loan balance to cure such non-compliance ; (ii) maximum consolidated leverage ratio, which shall not be greater than 0.60 to 1.00 on any testing date; (iii) minimum consolidated liquidity, under which unrestricted consolidated cash and cash equivalents shall be no less than $25 million at any time and total consolidated cash and cash equivalents (including cash restricted under the Sinosure Credit Facility) shall not be less than the greater of $50 million or 5.0% of Total Indebtedness (as defined in the Sinosure Credit Facility) or $9 million (i.e., $1.5 million per each VLCC securing the Sinosure Credit Facility); and (iv) consolidated interest expense coverage ratio, which shall not be less than 2.50 to 1.00 for the period commencing on July 1, 2020 and shall be calculated on a trailing twelve-month basis. No event of default under this covenant will occur if the failure to comply is capable of remedy and is remedied within thirty days of the Facility Agent giving notice to the Company or (if earlier) any Obligor becoming aware of the failure to comply, and if such action is being taken with respect to a Test Date falling on or after January 1, 2021, then any such remedy and the form of the same shall be considered and determined by the lenders under the Sinosure Credit Facility in their absolute discretion . The 8.5% Senior Notes Indenture contains certain restrictive covenants, including covenants that, subject to certain exceptions and qualifications, restrict our ability to make certain payments if a default under the Indenture has occurred and is continuing or will result therefrom and require us to limit the amount of debt we incur, maintain a certain minimum net worth and provide certain reports. The Indenture also provides for certain customary events of default (subject, in certain cases, to receipt of notice of default and/or customary grace or cure periods). ​ Pursuant to the limitation on borrowings covenant, the Company shall not permit Total Borrowings (as defined in the Indenture) to equal or exceed 70% of Total Assets (as defined in the Indenture). The Company shall also ensure that Net Worth (defined as Total Assets, less Intangible assets and Total Borrowings, as defined in the Indenture) exceeds $600 million pursuant to the Minimum Net Worth covenant. ​ The Company’s credit facilities also require it to comply with a number of covenants, including the delivery of quarterly and annual financial statements, budgets and annual projections; maintaining required insurances; compliance with laws (including environmental); compliance with the Employee Retirement Income Security Act of 1974 ("ERISA"); maintenance of flag and class of the collateral vessels; restrictions on consolidations, mergers or sales of assets; limitations on liens; limitations on issuance of certain equity interests; limitations on transactions with affiliates; and other customary covenants and related provisions. ​ While the Company was in compliance with all of its debt covenants as of June 30, 2021, the currently forecasted decline in average daily TCE rates across all vessel classes during 2021 could cause the Company to breach the Interest Coverage Ratio covenant under the Core Term Loan Facility and the Sinosure Credit Facility at the end of the third quarter of 2021. If the Company breaches such covenant and is unable to remedy the relevant breach or obtain a waiver, the Company’s lenders could accelerate its debt and the lenders under the 2020 Debt Facilities and the Sinosure Credit Facility could foreclose on the 20 vessels pledged by the Company. The Company is in discussions with the Sinosure Credit Facility lenders with regard to amending the debt facilities to eliminate the Interest Coverage Ratio covenant. We believe that the Company will either obtain the lender’s consent to such an amendment or a waiver for this potential covenant breach by September 30, 2021. ​ Interest Expense ​ Total interest expense before the impact of capitalized interest, including amortization of issuance and deferred financing costs (for additional information related to deferred financing costs see Note 3, “Significant Accounting Policies”), commitment, administrative and other fees for all of the Company’s debt facilities for the three and six months ended June 30, 2021 was $6.9 million and $14.1 million, respectively, and for the three and six months ended June 30, 2020 was $8.7 million and $20.6 million, respectively. Interest paid for the Company’s debt facilities for the three and six months ended June 30, 2021 was $6.0 million and $12.3 million respectively, and for the three and six months ended June 30, 2020 was $10.2 million and $17.3 million respectively. ​ Debt Modifications, Repurchases and Extinguishments ​ During the first six months of 2020, the Company incurred debt issuance costs aggregating $7.3 million in connection with the 2020 Debt Facilities. Issuance costs paid to lenders and third-party fees associated with the Core Revolving Facility aggregating $0.8 million were capitalized as deferred finance charges. Issuance costs paid to lenders and third-party fees associated with Core Term Loan Facility and Transition Term Loan Facility totaled $6.5 million, of which $6.3 million were capitalized as deferred finance charges and $0.2 million associated with third-party fees paid that were deemed to be a modification were expensed and are included in third-party debt modification fees in the accompanying condensed consolidated statement of operations. Issuance costs incurred and capitalized as deferred finance charges have been treated as a reduction of debt proceeds. In addition, i n connection with the Company recognized aggregate net losses totaling The net losses reflect (i)

TAXES

TAXES	6 Months Ended
	Jun. 30, 2021
TAXES [Abstract]
TAXES	Note 11 — Taxes: ​ The Company derives substantially all of its gross income from the use and operation of vessels in international commerce. The Company’s entities that own and operate vessels are primarily domiciled in the Marshall Islands, which do not impose income tax on shipping operations. The Company also has or had subsidiaries in various jurisdictions that perform administrative, commercial or technical management functions. These subsidiaries are subject to income tax based on the services performed in countries in which their offices are located; current and deferred income taxes are recorded accordingly. ​ A substantial portion of income earned by the Company is not subject to income tax. With respect to subsidiaries not subject to income tax in their respective countries of incorporation, no deferred taxes are provided for the temporary differences in the bases of the underlying assets and liabilities for tax and accounting purposes. ​ The Company qualifies for an exemption from U.S. federal income taxes under Section 883 of the U.S. Internal Revenue Code of 1986, as amended (the “Code”) and U.S. Treasury Department regulations for the 2021 calendar year, as less than 50 percent of the total value of the Company’s stock was held by one or more shareholders who own 5% or more of the Company’s stock for more than half of the days of 2021. ​ The Marshall Islands imposes tonnage taxes, which are assessed on the tonnage of certain of the Company’s vessels. These tonnage taxes are included in vessel expenses in the accompanying condensed consolidated statements of operations.

CAPITAL STOCK AND STOCK COMPENS

CAPITAL STOCK AND STOCK COMPENSATION	6 Months Ended
	Jun. 30, 2021
CAPITAL STOCK AND STOCK COMPENSATION [Abstract]
CAPITAL STOCK AND STOCK COMPENSATION	Note 12 — Capital Stock and Stock Compensation: ​ The Company accounts for stock-based compensation expense in accordance with the fair value method required by ASC 718, Compensation – Stock Compensation ​ Issuance of Shares upon Merger ​ At the Effective Time, the Diamond S Common Shares issued and outstanding immediately prior to the Effective Time (excluding Diamond S Common Shares owned by Diamond S, the Company, Merger Sub or any of their respective direct or indirect wholly-owned subsidiaries) were cancelled in exchange for 0.55375 of a share of INSW Common Stock and cash payable in respect of fractional shares. The aforementioned 0.55375 exchange ratio set forth in the Merger Agreement resulted in the issuance of 22,536,647 shares of INSW Common Stock with the pre-merger INSW shareholders and the former Diamond S shareholders owning approximately 55.75% and 44.25% , respectively, of the 50,674,393 issued and outstanding common stock of the Company immediately following the Effective Time. ​ Restricted Common Stock The Company awarded a total of 41,287 restricted common stock shares during the six months ended June 30, 2021 to its non-employee directors. The weighted average fair value of INSW’s stock on the measurement date of such awards was $19.86 per share. Such restricted share awards vest in full on the earlier of the next annual meeting of the stockholders or June 2, 2022, subject to each director continuing to provide services to INSW through such date. The restricted share awards granted may not be transferred, pledged, assigned or otherwise encumbered prior to vesting. Prior to the vesting date, a holder of restricted share awards otherwise has all the rights of a shareholder of INSW, including the right to vote such shares and the right to receive dividends paid with respect to such shares at the same time as common shareholders generally. ​ After giving effect to the exchange ratio and appropriate adjustments to reflect the consummation of the Merger, outstanding awards of 131,845 unvested Diamond S restricted stock, as of the Effective Time, were assumed by the Company and converted into 72,994 of unvested restricted shares with respect to INSW Common Stock, on the same general terms and conditions under the applicable Diamond S plans and award agreements in effect immediately prior to the Effective Time. ​ Effective as of the Effective Time, as contemplated by the Merger Agreement in order to permit three directors designated by Diamond S to serve on the Board, Mr. Ty E. Wallach resigned as a member of the Board. In connection with his resignation from the Board, the Board approved the accelerated vesting of his 5,035 share grant of restricted INSW Common Stock made in June 2021. ​ Restricted Stock Units and Stock Options ​ During the six months ended June 30, 2021, the Company granted 64,943 time-based restricted stock units (“RSUs”) to certain of its senior officers and employees. The weighted average grant date fair value of these awards was $21.58 per RSU. Each RSU represents a contingent right to receive one share of INSW common stock upon vesting. Each award of RSUs will vest in equal installments on each of the first three anniversaries of the grant date. ​ During the six months ended June 30, 2021, the Company awarded 64,943 performance-based RSUs to certain of its senior officers and employees. Each performance stock unit represents a contingent right to receive RSUs based upon the covered employees being continuously employed through the end of the period over which the performance goals are measured and shall vest as follows: (i) one ​ During the six months ended June 30, 2021, the Company awarded to certain of its senior officers and employees an aggregate of 141,282 stock options. Each stock option represents an option to purchase one share of INSW common stock for an exercise price of $21.58 per share. Each stock option will vest in equal installments on each of the first three anniversaries of the award date. The weighted average grant date fair value of the options was $9.92 per option. The fair value of the options was estimated using the Black-Scholes option pricing model with inputs that include the INSW stock price, the INSW exercise price and the following weighted average assumptions: risk free interest rates of 1.06%, dividend yields of 1.23%, expected stock price volatility factor of .55, and expected lives at inception of six years. Stock options may not be transferred, pledged, assigned or otherwise encumbered prior to vesting. The stock options expire on the business day immediately preceding the tenth anniversary of the award date. If a stock option grantee’s employment is terminated for cause (as defined in the applicable Form of Grant Agreement), stock options (whether then vested or exercisable or not) will lapse and will not be exercisable. If a stock option grantee’s employment is terminated for reasons other than cause, the option recipient may exercise the vested portion of the stock option but only within such period of time ending on the earlier to occur of (i) the 90th day ending after the option recipient’s employment terminated and (ii) the expiration of the options, provided that if the optionee’s employment terminates for death or disability the vested portion of the option may be exercised until the earlier of (a) the first anniversary of employment termination and (b) the expiration date of the options. ​ Dividends ​ On February 23, 2021, and June 4, 2021, the Company’s Board of Directors declared regular quarterly cash dividends of $0.06 per share. Pursuant to these declarations, the Company made dividend payments totaling $1.7 million on each of March 26, 2021 and June 28, 2021, respectively, to stockholders of record as of March 11, 2021 and June 14, 2021, respectively. The Company’s Board of Directors declared a regular quarterly cash dividend of $0.06 per share of common stock on July 28, 2021. The dividend will be paid on September 23, 2021 to shareholders of record as of September 9, 2021. ​ See Note 2, “Merger Transaction” for a description of the special dividend aggregating $31.5 million that was paid on July 15, 2021. ​ Share Repurchases ​ In connection with the settlement of vested restricted stock units, the Company repurchased 28,145 and 50,975 shares of common stock during the three and six months ended June 30, 2021, respectively, at an average cost of $19.23 and $20.21, respectively, per share (based on the market prices on the dates of vesting) from certain members of management to cover withholding taxes. Similarly, the Company repurchased 23,744 and 56,954 shares of common stock during the three and six months ended June 30, 2020, respectively, at an average cost of $20.84 and $21.07, respectively, per share (based on the market prices on the dates of vesting) from certain members of management to cover withholding taxes. ​ On August 4, 2020, the Company’s Board of Directors approved a resolution reauthorizing the Company’s $30.0 million stock repurchase program for another 24-month period ending August 4, 2022, on the open market or otherwise, in such quantities, at such prices, in such manner and on such terms and conditions as management determines is in the best interests of the Company. Shares owned by employees, directors and other affiliates of the Company are not eligible for repurchase under this program without further authorization from the Board. On October 28, 2020, the Company’s Board of Directors authorized an increase in the share repurchase program from $30.0 million to $50.0 million. No shares were acquired under repurchase programs during the six months ended June 30, 2021. Under a prior existing stock repurchase program, the Company repurchased and retired 1,417,292 shares of its common stock in open-market purchases, at an average price of $21.16 per share, for a total cost of $30.0 million, during the six months ended June 30, 2020. ​ ​

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	6 Months Ended
	Jun. 30, 2021
ACCUMULATED OTHER COMPREHENSIVE LOSS [Abstract]
ACCUMULATED OTHER COMPREHENSIVE LOSS	Note 13 — Accumulated Other Comprehensive Loss: ​ The components of accumulated other comprehensive loss, net of related taxes, in the condensed consolidated balance sheets follow: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 December 31, 2020 Unrealized losses on derivative instruments ​ $ (14,276) ​ $ (24,098) Items not yet recognized as a component of net periodic benefit cost (pension plans) ​ ​ (8,641) ​ ​ (8,515) ​ ​ $ (22,917) ​ $ (32,613) ​ ​ The changes in the balances of each component of accumulated other comprehensive loss, net of related taxes, during the three and six months ended June 30, 2021 and 2020 follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Unrealized losses on cash flow hedges ​ Items not yet recognized as a component of net periodic benefit cost ​ Total Balance as of March 31, 2021 ​ $ (13,815) ​ $ (8,579) ​ $ (22,394) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ (3,431) ​ ​ (62) ​ ​ (3,493) Amounts reclassified from accumulated other comprehensive loss ​ ​ 2,970 ​ ​ — ​ ​ 2,970 Balance as of June 30, 2021 ​ $ (14,276) ​ $ (8,641) ​ $ (22,917) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of March 31, 2020 ​ $ (26,717) ​ $ (8,245) ​ $ (34,962) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ (2,828) ​ ​ 64 ​ ​ (2,764) Amounts reclassified from accumulated other comprehensive loss ​ ​ 1,645 ​ ​ — ​ ​ 1,645 Balance as of June 30, 2020 ​ $ (27,900) ​ $ (8,181) ​ $ (36,081) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Unrealized losses on cash flow hedges ​ Items not yet recognized as a component of net periodic benefit cost ​ Total Balance as of December 31, 2020 ​ $ (24,098) ​ $ (8,515) ​ $ (32,613) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ 3,849 ​ ​ (126) ​ ​ 3,723 Amounts reclassified from accumulated other comprehensive loss ​ ​ 5,973 ​ ​ — ​ ​ 5,973 Balance as of June 30, 2021 ​ $ (14,276) ​ $ (8,641) ​ $ (22,917) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of December 31, 2019 ​ $ (11,732) ​ $ (8,838) ​ $ (20,570) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ (18,949) ​ ​ 657 ​ ​ (18,292) Amounts reclassified from accumulated other comprehensive loss ​ ​ 2,781 ​ ​ — ​ ​ 2,781 Balance as of June 30, 2020 ​ $ (27,900) ​ $ (8,181) ​ $ (36,081) ​ ​ Amounts reclassified out of each component of accumulated other comprehensive loss follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ ​ (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 ​ Statement of Operations Reclassifications of losses on cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps entered into by the Company's ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity in income of equity method joint venture investees ​ $ 261 ​ $ 228 ​ $ 555 ​ $ 388 ​ affiliated companies Interest rate swaps entered into by the Company's subsidiaries ​ ​ 1,149 ​ ​ 1,417 ​ ​ 2,265 ​ ​ 2,312 ​ Interest expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reclassifications of losses on derivatives subsequent to ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ discontinuation of hedge accounting ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate collar entered into by the Company's subsidiaries ​ ​ — ​ ​ — ​ ​ — ​ ​ 81 ​ Interest expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reclassifications of losses on other-than-insignificant ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps entered into by the Company's subsidiaries ​ ​ 1,560 ​ ​ — ​ ​ 3,153 ​ ​ — ​ Interest expense Total before and net of tax ​ $ 2,970 ​ $ 1,645 ​ $ 5,973 ​ $ 2,781 ​ ​ ​ At June 30, 2021, the Company expects that it will reclassify $8.9 million (gross and net of tax) of net losses on derivative instruments from accumulated other comprehensive loss to earnings during the next twelve months due to the payment of variable rate interest associated with floating rate debt of INSW’s equity method investees and the interest rate swaps held by the Company. ​ See Note 9, “Fair Value of Financial Instruments, Derivatives and Fair Value Disclosures,” for additional disclosures relating to derivative instruments.

REVENUE

REVENUE	6 Months Ended
	Jun. 30, 2021
REVENUE [Abstract]
REVENUE	Note 14 — Revenue: ​ Revenue Recognition ​ The majority of the Company's contracts for pool revenues, time and bareboat charter revenues, and voyage charter revenues are accounted for as lease revenue under ASC 842. The Company's contracts with pools are short term which are cancellable with up to 90 days' notice. As of June 30, 2021, the Company is a party to time charter out contracts with customers on five Panamaxes, one LR2, and one VLCC with expiry dates ranging from July 2021 to March 2023. Upon its expiry in July 2021, the Company extended one of the Panamaxes for an additional three months through October 2021. The Company is a party to a short-term profit share agreement to participate in a share of the profits and losses generated from a chartered-in MR commercially managed by a pool in which the Company participates. The Company’s share of earnings and charter hire expenses from this profit share agreement are included in voyage charter revenues and charter hire expenses, respectively, in the accompanying condensed consolidated statements of operations. The Company's contracts with customers for voyage charters are short term and vary in length based upon the duration of each voyage. Lease revenue for non-variable lease payments are recognized over the lease term on a straight-line basis and lease revenue for variable lease payments (e.g., demurrage) are recognized in the period in which the changes in facts and circumstances on which the variable lease payments are based occur. ​ Lightering services provided by the Company's Crude Tanker Lightering Business, and voyage charter contracts that do not meet the definition of a lease are accounted for as service revenues under ASC 606. In accordance with ASC 606, revenue is recognized when a customer obtains control of or consumes promised services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled to receive in exchange for these services. ​ The following table presents the Company’s revenues from leases accounted for under ASC 842 and revenues from services accounted for under ASC 606 for the three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Totals Three months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 15,245 ​ $ 11,210 ​ $ 26,455 Time and bareboat charter revenues ​ ​ 10,076 ​ ​ 1,638 ​ ​ 11,714 Voyage charter revenues from non-variable lease payments ​ ​ 787 ​ ​ 908 ​ ​ 1,695 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 6,440 ​ ​ — ​ ​ 6,440 Total shipping revenues ​ $ 32,548 ​ $ 13,756 ​ $ 46,304 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 72,446 ​ $ 27,613 ​ $ 100,059 Time and bareboat charter revenues ​ ​ 26,655 ​ ​ — ​ ​ 26,655 Voyage charter revenues from non-variable lease payments ​ ​ 2,690 ​ ​ 1,705 ​ ​ 4,395 Voyage charter revenues from variable lease payments ​ ​ 50 ​ ​ — ​ ​ 50 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 8,566 ​ ​ — ​ ​ 8,566 Total shipping revenues ​ $ 110,407 ​ $ 29,318 ​ $ 139,725 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Totals Six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 32,903 ​ $ 18,211 ​ $ 51,114 Time and bareboat charter revenues ​ ​ 23,154 ​ ​ 3,258 ​ ​ 26,412 Voyage charter revenues from non-variable lease payments (1) ​ ​ 1,727 ​ ​ 1,482 ​ ​ 3,209 Voyage charter revenues from variable lease payments ​ ​ — ​ ​ 51 ​ ​ 51 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 12,274 ​ ​ — ​ ​ 12,274 Total shipping revenues ​ $ 70,058 ​ $ 23,002 ​ $ 93,060 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 142,696 ​ $ 58,572 ​ $ 201,268 Time and bareboat charter revenues ​ ​ 35,259 ​ ​ — ​ ​ 35,259 Voyage charter revenues from non-variable lease payments ​ ​ 10,043 ​ ​ 2,406 ​ ​ 12,449 Voyage charter revenues from variable lease payments ​ ​ 1,170 ​ ​ — ​ ​ 1,170 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 14,916 ​ ​ — ​ ​ 14,916 Total shipping revenues ​ $ 204,084 ​ $ 60,978 ​ $ 265,062 (1) Includes $0.5 million of loss of hire proceeds received during the first quarter of 2021 . ​ Contract Balances ​ The following table provides information about receivables, contract assets and contract liabilities from contracts with customers, and significant changes in contract assets and liabilities balances, associated with revenue from services accounted for under ASC 606. Balances related to revenues from leases accounted for under ASC 842 are excluded from the table below. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Voyage receivables - Billed receivables ​ Contract assets (Unbilled voyage receivables) ​ Contract liabilities (Deferred revenues and off hires) Opening balance as of January 1, 2021 ​ $ 2,148 ​ $ 166 ​ $ — Closing balance as of June 30, 2021 ​ ​ 3,107 ​ ​ 125 ​ ​ — ​ We receive payments from customers based on the schedule established in our contracts. Contract assets relate to our conditional right to consideration for our completed performance obligations under contracts and decrease when the right to consideration becomes unconditional or payments are received. Contract liabilities include payments received in advance of performance under contracts and are recognized when performance under the respective contract has been completed. Deferred revenues allocated to unsatisfied performance obligations will be recognized over time as the services are performed. ​ Performance Obligations ​ All of the Company’s performance obligations, and associated revenue, are generally transferred to customers over time. The expected duration of services is less than one year. Adjustments in revenues from performance obligations satisfied in previous periods recognized were nil, respectively, during the three and six months ended June 30, 2021, compared with nil and $15 thousand, respectively, during the three and six months ended June 30, 2020. These adjustments to revenue were related to changes in estimates of performance obligations related to voyage charters. ​ Costs to Obtain or Fulfill a Contract ​ As of June 30, 2021, there were no unamortized deferred costs of obtaining or fulfilling a contract.

LEASES

LEASES	6 Months Ended
	Jun. 30, 2021
LEASES [Abstract]
LEASES	Note 15 — Leases: ​ As permitted under ASC 842, the Company has elected not to apply the provisions of ASC 842 to short term leases, which include: (i) tanker vessels chartered-in where the duration of the charter was one year or less at inception; (ii) workboats employed in the Crude Tankers Lightering business which have a lease term of 12-months or less; and (iii) short term leases of office and other space. ​ ​ Contracts under which the Company is a Lessee ​ The Company currently has two major categories of leases - chartered-in vessels and leased office and other space. The expenses recognized during the three and six months ended June 30, 2021 and 2020 for the lease component of these leases are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Operating lease cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Charter hire expenses ​ $ 2,470 ​ $ 2,977 ​ $ 4,891 ​ $ 6,705 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Office and other space ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ General and administrative ​ ​ 274 ​ ​ 257 ​ ​ 547 ​ ​ 506 Voyage expenses ​ ​ 42 ​ ​ 42 ​ ​ 84 ​ ​ 84 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term lease cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel assets (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Charter hire expenses ​ ​ 1,055 ​ ​ 1,126 ​ ​ 1,956 ​ ​ 2,926 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Office and other space ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ General and administrative ​ ​ — ​ ​ — ​ ​ — ​ ​ 29 Total lease cost ​ $ 3,841 ​ $ 4,402 ​ $ 7,478 ​ $ 10,250 (1) Excludes vessels spot chartered-in under operating leases and employed in the Crude Tankers Lightering business for periods of less than one month each, totaling $0.1 million and $0.3 million for the three and six months ended June 30, 2021, respectively, compared with $0.1 million and $0.2 million for the three and six months ended June 30, 2020, respectively , including both lease and non-lease components. ​ Supplemental cash flow information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 Cash paid for amounts included in the measurement of lease liabilities ​ ​ ​ ​ ​ ​ Operating cash flows used for operating leases ​ $ 5,522 ​ $ 7,295 ​ Supplemental balance sheet information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 ​ December 31, 2020 Operating lease right-of-use assets ​ $ 16,999 ​ $ 21,588 ​ ​ ​ ​ ​ ​ ​ Current portion of operating lease liabilities ​ $ (7,226) ​ $ (8,867) Long-term operating lease liabilities ​ ​ (7,541) ​ ​ (10,253) Total operating lease liabilities ​ $ (14,767) ​ $ (19,120) ​ ​ ​ ​ ​ ​ ​ Weighted average remaining lease term - operating leases ​ ​ 2.45 years ​ ​ 2.75 years Weighted average discount rate - operating leases ​ ​ 6.98% ​ ​ 7.21% ​ 1. Charters-in of vessel assets: ​ As of June 30, 2021, INSW had commitments to charter in two Aframaxes, one LR1 and one workboat employed in the Crude Tankers Lightering business. and the others are time charters with expiry dates ranging from August 2021 to December 2021 accounted for as operating leases. The Company’s bareboat charters contain purchase options commencing in the first quarter of 2021. As of June 30, 2021, the Company has determined that the purchase options are not reasonably certain of being exercised. Lease liabilities related to time charters-in vessels exclude estimated days that the vessels will not be available for employment due to drydock because the Company does not pay charter hire when time chartered-in vessels are not available for its use. ​ Payments of lease liabilities and related number of operating days under these operating leases as of June 30, 2021 are as follows: ​ Bareboat Charters-in: ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Amount ​ Operating Days 2021 ​ $ 3,165 ​ 368 2022 ​ ​ 6,278 ​ 730 2023 ​ ​ 4,532 ​ 556 Total lease payments ​ ​ 13,975 ​ 1,654 less imputed interest ​ ​ (1,092) ​ ​ Total operating lease liabilities ​ $ 12,883 ​ ​ ​ Time Charters-in: ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Amount ​ Operating Days 2021 ​ $ 975 ​ 229 Total lease payments (lease component only) ​ ​ 975 ​ 229 less imputed interest ​ ​ (4) ​ ​ Total operating lease liabilities ​ $ 971 ​ ​ ​ 2. Office and other space: ​ The Company has operating leases for offices and lightering workboat dock space. These leases have expiry dates ranging from August 2021 to December 2024. The lease for the workboat dock space contains renewal options executable by the Company for periods through December 2027. We have determined that the options through December 2024 are reasonably certain to be executed by the Company, and accordingly the options are included in the lease liability and right of use asset calculations for such lease. ​ Payments of lease liabilities for office and other space as of June 30, 2021 are as follows: ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Amount 2021 ​ $ 302 2022 ​ ​ 273 2023 ​ ​ 229 2024 ​ ​ 178 Total lease payments ​ ​ 982 less imputed interest ​ ​ (69) Total operating lease liabilities ​ $ 913 ​ Contracts under which the Company is a Lessor ​ See Note 14, “Revenue,” for discussion on the Company’s revenues from operating leases accounted for under ASC 842. ​ ​ The future minimum revenues, before reduction for brokerage commissions, expected to be received on non-cancelable time charters for five Panamaxes, one LR2, and one VLCC and the related revenue days as of June 30, 2021 are as follows: ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Amount ​ Revenue Days 2021 ​ $ 11,706 ​ 499 2022 ​ ​ 16,425 ​ 365 2023 ​ ​ 3,195 ​ 71 Future minimum revenues ​ $ 31,326 ​ 935 ​ Future minimum revenues do not include (i) the Company’s share of time charters entered into by the pools in which it participates, and (ii) the Company’s share of time charters entered into by the joint ventures, which the Company accounts for under the equity method. Revenues from a time charter are not generally received when a vessel is off-hire, including time required for normal periodic maintenance of the vessel. In arriving at the minimum future charter revenues, an estimated time off-hire to perform periodic maintenance on each vessel has been deducted, although there is no assurance that such estimate will be reflective of the actual off-hire in the future.

CONTINGENCIES

CONTINGENCIES	6 Months Ended
	Jun. 30, 2021
CONTINGENCIES [Abstract]
CONTINGENCIES	Note 16 — Contingencies: ​ INSW’s policy for recording legal costs related to contingencies is to expense such legal costs as incurred. ​ Multi-Employer Plans ​ The Merchant Navy Officers Pension Fund (“MNOPF”) is a multi-employer defined benefit pension plan covering British crew members that served as officers on board INSW’s vessels (as well as vessels of other owners). The trustees of the plan have indicated that, under the terms of the High Court ruling in 2005, which established the liability of past employers to fund the deficit on the Post 1978 section of MNOPF, calls for further contributions may be required if additional actuarial deficits arise or if other employers liable for contributions are not able to pay their share in the future. As the amount of any such assessment cannot be reasonably estimated, no reserves have been recorded for this contingency in INSW’s consolidated financial statements as of June 30, 2021. The deficit valuation as of March 31, 2021, is expected to be issued during 2022. The Merchant Navy Ratings Pension Fund (“MNRPF”) is a multi-employer defined benefit pension plan covering British crew members that served as ratings (seamen) on board INSW’s vessels (as well as vessels of other owners) more than 20 years ago. Participating employers include current employers, historic employers that have made voluntary contributions, and historic employers such as INSW that have made no deficit contributions. Calls for contributions may be required if additional actuarial deficits arise or if other employers liable for contributions are unable to pay their share in the future. As the amount of any such assessment cannot be reasonably estimated, no reserves have been recorded in INSW’s consolidated financial statements as of June 30, 2021. The next deficit valuation will be as of March 31, 2023. ​ Spin-Off Related Agreements On November 30, 2016, INSW was spun off from OSG as a separate publicly traded company. In connection with the spin-off, INSW and OSG entered into several agreements, including a separation and distribution agreement, an employee matters agreement and a transition services agreement. While most of the obligations under those agreements were subsequently fulfilled, certain provisions (including in particular mutual indemnification provisions under the separation and distribution agreement and the employee matters agreement) continue in force. ​ Legal Proceedings Arising in the Ordinary Course of Business ​ The Company is a party, as plaintiff or defendant, to various suits in the ordinary course of business for monetary relief arising principally from personal injuries, wrongful death, collision or other casualty and to claims arising under charter parties and other contract disputes. A substantial majority of such personal injury, wrongful death, collision or other casualty claims against the Company are covered by insurance (subject to deductibles not material in amount). Each of the claims involves an amount which, in the opinion of management, should not be material to the Company’s financial position, results of operations and cash flows.

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Cash, cash equivalents and restricted cash	Cash, cash equivalents and restricted cash —
Concentration of Credit Risk	Concentration of Credit Risk — ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Allowance for Credit Losses - Balance at December 31, 2020 ​ $ 55 Provision for expected credit losses ​ ​ 43 Write-offs charged against the allowance ​ ​ (3) Balance at June 30, 2021 ​ $ 95 ​ We are also exposed to credit losses from off-balance sheet exposures related to guarantees of joint venture debt. See Note 7, “Equity Method Investments,” for more information on these off-balance sheet exposures. ​ During the three and six months ended June 30, 2021 and 2020, the Company did not have any individual customers who accounted for 10% or more of its revenues apart from the pools in which it participates. The pools in which the Company participates accounted in aggregate for 94% and 88% of consolidated voyage receivables at June 30, 2021 and December 31, 2020, respectively.
Deferred finance charges	Deferred finance charges — Revolving Facility (See Note 10, “Debt”) as of June 30, 2021 and December 31, 2020, respectively, are included in other assets in the condensed consolidated balance sheets. Unamortized deferred financing charges of $5.9 million and $6.9 million relating to the Company’s outstanding debt facilities as of June 30, 2021 and December 31, 2020, respectively, are included in long-term debt in the condensed consolidated balance sheets. Interest expense relating to the amortization of deferred financing charges amounted to $0.5 million and $1.0 million for the three and six months ended June 30, 2021, respectively, and $0.7 million and $1.6 million for the three and six months ended June 30, 2020, respectively.
Vessels	Vessels —
Recently adopted / issued accounting standards	Recently Issued Accounting Standards Reference Rate Reform which provides relief for companies preparing for discontinuation of interest rates such as LIBOR. A contract modification is eligible to apply the optional relief to account for the modifications as a continuation of the existing contracts without additional analysis and consider embedded features to be clearly and closely related to the host contract without reassessment, if all of the following criteria are met: (1) contract references a rate that will be discontinued; (2) modified terms directly replace (or have potential to replace) this reference rate; and (3) changes to any other terms that change (or have potential to change) amount and timing of cash flows must be related to replacement of the reference rate. In addition, this guidance provides relief from certain hedge accounting requirements. Hedge accounting may continue uninterrupted when critical terms change due to reference rate reform. For cash flow hedges, entities can (1) disregard potential discontinuation of a referenced interest rate when assessing whether a hedged forecasted interest payment is probable; (2) continue hedge accounting upon a change in the hedged risk as long as the hedge is still highly effective; (3) assess effectiveness of the hedge relationship in ways that essentially disregards a potential mismatch in the variable rate indices between the hedging instrument and the hedged item; and (4) disregard the requirement that individual hedged transactions must share the same risk exposure for hedges of portfolios of forecasted transactions that reference a rate affected by reference rate reform. Relief provided by this ASU is optional and expires December 31, 2022. In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (ASC 848) to refine the scope of ASC 848 and to clarify some of its guidance. The Company has determined that its primary exposure to LIBOR is in relation to its floating rate debt facilities and the interest rate derivatives to which it is a party. On November 30, 2020, the benchmark administrator for the U.S. Dollar (“USD”) LIBOR announced a proposal to extend the publication of the most commonly used USD LIBOR settings until June 30, 2023. In light of this proposal, in an interagency statement, the Board of Governors of the Federal Reserve System, the Federal Deposit Insurance Corporation, and the Office of the Comptroller of the Currency issued guidance, strongly encouraging banks to cease entering into new contracts that use USD LIBOR as a reference rate as soon as practicable and in any event by December 31, 2021. Only in limited circumstances will it be appropriate for banks to enter into new contracts referencing USD LIBOR after December 31, 2021. The principal objective, and result, of these actions appears to be that legacy USD LIBOR-based instruments (i.e., those maturing after December 31, 2021) may continue to use USD LIBOR as a reference rate through June 30, 2023, without undermining the regulators’ determination that LIBOR should not be available for any other purpose. On January 25, 2021, the International Swaps and Derivatives Association, Inc. (“ISDA”), published new fallback provisions for derivatives linked to key interbank offered rates (“IBOR”) which will be incorporated into all new derivatives contracts that reference ISDA’s standard interest rate derivatives definitions. Such fallback provisions will also be included in legacy non-cleared derivatives if the counterparties have bilaterally agreed to include them or both have adhered to the IBOR fallback protocol. The Company has engaged and will continue to engage in discussions with its lending banks and the counterparties to its interest rate derivative contracts in advance of the June 30, 2023 sunset date for the USD LIBOR reference rate settings used in its agreements to evaluate the Company’s options. Based on information available today, the Company’s current view is that the Secured Overnight Financing Rate (“SOFR”) will be the alternative reference rate that the Company’s LIBOR-based agreements will transition to as the sunset date draws closer.

CONTINGENCIES (Policy)

CONTINGENCIES (Policy)	6 Months Ended
	Jun. 30, 2021
CONTINGENCIES [Abstract]
Legal costs	​ INSW’s policy for recording legal costs related to contingencies is to expense such legal costs as incurred.

SIGNIFICANT ACCOUNTING POLICI_2

SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Jun. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Activity for allowance for credit losses	​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Allowance for Credit Losses - Balance at December 31, 2020 ​ $ 55 Provision for expected credit losses ​ ​ 43 Write-offs charged against the allowance ​ ​ (3) Balance at June 30, 2021 ​ $ 95

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	6 Months Ended
	Jun. 30, 2021
EARNINGS PER COMMON SHARE [Abstract]
Components of Calculation of Earnings Per Share	Reconciliations of the numerator of the basic and diluted earnings per share computations are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Net (loss)/income allocated to: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common Stockholders ​ $ (18,785) ​ $ 64,272 ​ $ (32,154) ​ $ 97,227 Participating securities ​ ​ 2 ​ ​ 86 ​ ​ 6 ​ ​ 150 ​ ​ $ (18,783) ​ $ 64,358 ​ $ (32,148) ​ $ 97,377

BUSINESS AND SEGMENT REPORTING

BUSINESS AND SEGMENT REPORTING (Tables)	6 Months Ended
	Jun. 30, 2021
BUSINESS AND SEGMENT REPORTING [Abstract]
Schedule of Segment Reporting Information, by Segment	​ Information about the Company’s reportable segments as of and for the three and six months ended June 30, 2021 and 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Other ​ Totals Three months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 32,548 ​ $ 13,756 ​ $ — ​ $ 46,304 Time charter equivalent revenues ​ ​ 31,096 ​ ​ 13,622 ​ ​ — ​ ​ 44,718 Depreciation and amortization ​ ​ 13,039 ​ ​ 4,022 ​ ​ 18 ​ ​ 17,079 Loss on disposal of vessels and other property, including impairments ​ ​ 4,005 ​ ​ — ​ ​ — ​ ​ 4,005 Adjusted (loss)/income from vessel operations ​ ​ (7,058) ​ ​ 975 ​ ​ (18) ​ ​ (6,101) Equity in income of affiliated companies ​ ​ 5,375 ​ ​ — ​ ​ — ​ ​ 5,375 Investments in and advances to affiliated companies at June 30, 2021 ​ ​ 142,171 ​ ​ 7,409 ​ ​ — ​ ​ 149,580 Adjusted total assets at June 30, 2021 ​ ​ 1,122,807 ​ ​ 251,310 ​ ​ — ​ ​ 1,374,117 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 110,407 ​ $ 29,318 ​ $ — ​ $ 139,725 Time charter equivalent revenues ​ ​ 105,890 ​ ​ 29,399 ​ ​ — ​ ​ 135,289 Depreciation and amortization ​ ​ 14,732 ​ ​ 4,125 ​ ​ 23 ​ ​ 18,880 Loss on disposal of vessels and other property, including impairments ​ ​ 4,134 ​ ​ — ​ ​ — ​ ​ 4,134 Adjusted income/(loss) from vessel operations ​ ​ 62,883 ​ ​ 15,731 ​ ​ (23) ​ ​ 78,591 Equity in income of affiliated companies ​ ​ 5,205 ​ ​ — ​ ​ — ​ ​ 5,205 Investments in and advances to affiliated companies at June 30, 2020 ​ ​ 146,861 ​ ​ 8,330 ​ ​ — ​ ​ 155,191 Adjusted total assets at June 30, 2020 ​ ​ 1,288,235 ​ ​ 321,530 ​ ​ — ​ ​ 1,609,765 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Other ​ Totals Six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 70,058 ​ $ 23,002 ​ $ — ​ $ 93,060 Time charter equivalent revenues ​ ​ 67,046 ​ ​ 22,841 ​ ​ — ​ ​ 89,887 Depreciation and amortization ​ ​ 26,042 ​ ​ 7,750 ​ ​ 41 ​ ​ 33,833 Loss on disposal of vessels and other property, including impairments ​ ​ 4,016 ​ ​ — ​ ​ — ​ ​ 4,016 Adjusted loss from vessel operations ​ ​ (8,015) ​ ​ (1,698) ​ ​ (41) ​ ​ (9,754) Equity in income of affiliated companies ​ ​ 10,843 ​ ​ — ​ ​ — ​ ​ 10,843 Expenditures for vessels and vessel improvements ​ ​ 22,359 ​ ​ 1,771 ​ ​ — ​ ​ 24,130 Payments for drydocking ​ ​ 7,992 ​ ​ 6,728 ​ ​ — ​ ​ 14,720 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shipping revenues ​ $ 204,084 ​ $ 60,978 ​ $ — ​ $ 265,062 Time charter equivalent revenues ​ ​ 194,744 ​ ​ 60,276 ​ ​ — ​ ​ 255,020 Depreciation and amortization ​ ​ 28,977 ​ ​ 8,123 ​ ​ 47 ​ ​ 37,147 Loss on disposal of vessels and other property, including impairments ​ ​ 1,330 ​ ​ — ​ ​ — ​ ​ 1,330 Adjusted income/(loss) from vessel operations ​ ​ 106,824 ​ ​ 30,087 ​ ​ (47) ​ ​ 136,864 Equity in income of affiliated companies ​ ​ 10,316 ​ ​ — ​ ​ — ​ ​ 10,316 Expenditures for vessels and vessel improvements ​ ​ 22,451 ​ ​ 18,498 ​ ​ — ​ ​ 40,949 Payments for drydockings ​ ​ 12,121 ​ ​ 392 ​ ​ — ​ ​ 12,513 ​
Reconciliation of Revenue from Segments to Consolidated	​ Reconciliations of time charter equivalent (“TCE”) revenues of the segments to shipping revenues as reported in the condensed statements of operations follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Time charter equivalent revenues ​ $ 44,718 ​ $ 135,289 ​ $ 89,887 ​ $ 255,020 Add: Voyage expenses ​ ​ 1,586 ​ ​ 4,436 ​ ​ 3,173 ​ ​ 10,042 Shipping revenues ​ $ 46,304 ​ $ 139,725 ​ $ 93,060 ​ $ 265,062 ​
Reconciliation of Operating Profit (Loss) from Segments to Consolidated	Reconciliations of adjusted (loss)/income from vessel operations of the segments to (loss)/income before income taxes, as reported in the condensed consolidated statements of operations follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Total adjusted (loss)/income from vessel operations of all segments ​ $ (6,101) ​ $ 78,591 ​ $ (9,754) ​ $ 136,864 General and administrative expenses ​ ​ (6,829) ​ ​ (6,694) ​ ​ (14,969) ​ ​ (14,128) Provision for credit losses, net ​ ​ (2) ​ ​ 129 ​ ​ (43) ​ ​ 67 Third-party debt modification fees ​ ​ — ​ ​ — ​ ​ — ​ ​ (232) Merger and integration related costs ​ ​ (481) ​ ​ — ​ ​ (481) ​ ​ — Loss on disposal of vessels and other property, including impairments ​ ​ (4,005) ​ ​ (4,134) ​ ​ (4,016) ​ ​ (1,330) Consolidated (loss)/income from vessel operations ​ ​ (17,418) ​ ​ 67,892 ​ ​ (29,263) ​ ​ 121,241 Equity in income of affiliated companies ​ ​ 5,375 ​ ​ 5,205 ​ ​ 10,843 ​ ​ 10,316 Other income/(expense) ​ ​ 267 ​ ​ 143 ​ ​ 559 ​ ​ (13,289) Interest expense ​ ​ (7,006) ​ ​ (8,881) ​ ​ (14,286) ​ ​ (20,890) (Loss)/income before income taxes ​ $ (18,782) ​ $ 64,359 ​ $ (32,147) ​ $ 97,378 ​
Reconciliation of Assets from Segment to Consolidated	Reconciliations of total assets of the segments to amounts included in the condensed consolidated balance sheets follow: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 ​ June 30, 2020 Adjusted total assets of all segments ​ $ 1,374,117 ​ $ 1,609,765 Corporate unrestricted cash and cash equivalents ​ ​ 117,391 ​ ​ 128,063 Restricted cash ​ ​ 16,173 ​ ​ 16,398 Other unallocated amounts ​ ​ 11,184 ​ ​ 4,730 Consolidated total assets ​ $ 1,518,865 ​ $ 1,758,956

EQUITY METHOD INVESTMENTS (Tabl

EQUITY METHOD INVESTMENTS (Tables)	6 Months Ended
	Jun. 30, 2021
EQUITY METHOD INVESTMENTS [Abstract]
Results of Operations of Equity Method Investments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Shipping revenues ​ $ 26,109 ​ $ 26,119 ​ $ 51,954 ​ $ 52,143 Ship operating expenses ​ ​ (14,439) ​ ​ (14,241) ​ ​ (28,370) ​ ​ (28,481) Income from vessel operations ​ ​ 11,670 ​ ​ 11,878 ​ ​ 23,584 ​ ​ 23,662 Other (expense)/income ​ ​ (9) ​ ​ — ​ ​ (9) ​ ​ 40 Interest expense ​ ​ (1,098) ​ ​ (1,721) ​ ​ (2,310) ​ ​ (3,595) Income tax provision ​ ​ (981) ​ ​ (944) ​ ​ (1,973) ​ ​ (1,867) Net income ​ $ 9,582 ​ $ 9,213 ​ $ 19,292 ​ $ 18,240

VARIABLE INTEREST ENTITIES (V_2

VARIABLE INTEREST ENTITIES (VIEs)) (Tables)	6 Months Ended
	Jun. 30, 2021
VARIABLE INTEREST ENTITIES (VIEs) [Abstract]
Schedule of Variable Interest Entities	​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ ​ ​ Condensed Investments in Affiliated Companies ​ ​ ​ ​ $ 140,603
Schedule of Variable Interest Entities Liability in Condensed Consolidated Balance Sheet to Maximum Exposure to Loss	​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Condensed ​ Maximum Exposure to Other Liabilities ​ $ 3 ​ $ 173,853

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Tables)	6 Months Ended
	Jun. 30, 2021
FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES [Abstract]
Fair Value, by Balance Sheet Grouping	The estimated fair values of the Company’s financial instruments, other than derivatives that are not measured at fair value on a recurring basis, categorized based upon the fair value hierarchy, are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Fair Value ​ Level 1 ​ Level 2 June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents (1) ​ $ 133,564 ​ $ 133,564 ​ $ — Core Term Loan Facility ​ ​ (252,619) ​ ​ — ​ ​ (252,619) Sinosure Credit Facility ​ ​ (234,337) ​ ​ — ​ ​ (234,337) 8.5% Senior Notes ​ ​ (25,600) ​ ​ (25,600) ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents (1) ​ $ 215,677 ​ $ 215,677 ​ $ — Core Term Loan Facility ​ ​ (271,571) ​ ​ — ​ ​ (271,571) Sinosure Credit Facility ​ ​ (246,127) ​ ​ — ​ ​ (246,127) 8.5% Senior Notes ​ ​ (25,697) ​ ​ (25,697) ​ ​ — (1) Includes non-current restricted cash of $16.2 million and $16.3 million at June 30, 2021 and December 31, 2020, respectively. ​
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Long-term derivative ​ Current portion of derivative liabilities ​ Long-term derivative ​ Accounts payable, accrued expenses and other current liabilities ​ Other June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ 6,526 ​ $ (3,950) ​ $ (3,782) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (1) ​ ​ — ​ ​ — ​ ​ — ​ ​ (2,907) ​ ​ (12,628) Total ​ $ 6,526 ​ $ (3,950) ​ $ (3,782) ​ $ (2,907) ​ $ (12,628) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ 2,129 ​ $ (4,121) ​ $ (6,155) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (1) ​ ​ — ​ ​ — ​ ​ — ​ ​ (2,979) ​ ​ (14,051) Total ​ $ 2,129 ​ $ (4,121) ​ $ (6,155) ​ $ (2,979) ​ $ (14,051) (1) Represents the financing element of the hybrid instrument discussed above, which is recorded at amortized cost. ​
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Loss	​ The effect of cash flow hedging relationships recognized in other comprehensive income/(loss) excluding amounts reclassified from accumulated other comprehensive loss, including hedges of equity method investees, for the three and six months ended June 30, 2021 and 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ (2,981) ​ $ (2,828) ​ $ 4,765 ​ $ (18,949) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ ​ (450) ​ ​ — ​ ​ (916) ​ ​ — Total other comprehensive loss ​ $ (3,431) ​ $ (2,828) ​ $ 3,849 ​ $ (18,949) ​ ​ The effect of cash flow hedging relationships on the condensed consolidated statement of operations is presented excluding hedges of equity method investees. The effect of the Company’s cash flow hedging relationships on the condensed consolidated statement of operations for the three and six months ended June 30, 2021 and 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Derivatives designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ $ 1,149 ​ $ 1,417 ​ $ 2,265 ​ $ 2,312 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate collar ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,352 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other-than-insignificant financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps ​ ​ 1,560 ​ ​ — ​ ​ 3,153 ​ ​ — Total interest expense ​ $ 2,709 ​ $ 1,417 ​ $ 5,418 ​ $ 3,664 ​
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table presents the fair values, which are pre-tax, for assets and liabilities measured on a recurring basis (excluding investments in affiliated companies): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ ​ ​ Fair Value ​ Level 2 ​ Assets/(Liabilities) at June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative Assets (interest rate swaps) ​ ​ ​ ​ $ 6,526 ​ $ 6,526 (1) Derivative Liabilities (interest rate swaps) ​ ​ ​ ​ ​ (7,732) ​ ​ (7,732) (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets/(Liabilities) at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivative Assets (interest rate swaps) ​ ​ ​ ​ $ 2,129 ​ $ 2,129 (1) Derivative Liabilities (interest rate swaps) ​ ​ ​ ​ ​ (10,276) ​ ​ (10,276) (1) (1) For the interest rate swaps, fair values are derived using valuation models that utilize the income valuation approach. These valuation models take into account contract terms such as maturity, as well as other inputs such as interest rate yield curves and creditworthiness of the counterparty and the Company.
Schedule of Fair Value, Assets and Liabilities Measured on Nonrecurring Basis	The following table summarizes the fair values of assets for which an impairment charge was recognized for the three and six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Fair Value ​ ​ Level 2 ​ ​ Total Impairment Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude Tankers - Vessels held for sale (1)(2) ​ $ 6,542 ​ $ 6,542 ​ $ (3,497) (1) Pre-tax impairment charges of $3.5 million related to one Panamax in the Crude Tanker segment were recorded during the three-month period ended June 30, 2021. The held-for-sale impairment charges aggregating $3.5 million as of June 30, 2021 included a charge of $3.4 million to write the value of the vessel down to its estimated fair value, and estimated costs to sell the vessel of $0.1 million. (2) Fair value measurement of $6.5 million at June 30, 2021 used to determine the impairment for one Panamax was based upon a market approach, which considered the expected sale price of the vessel based on an executed memorandum of agreement for the sale of the vessel as discussed in Note 6, "Vessels." Because sales of vessels occur somewhat infrequently the expected sales prices are considered to be Level 2.

DEBT (Tables)

DEBT (Tables)	6 Months Ended
	Jun. 30, 2021
DEBT [Abstract]
Schedule of Long-term Debt Instruments	​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 December 31, 2020 Core Term Loan Facility, due 2025, net of unamortized deferred finance costs of $3,500 and $4,145 ​ $ 249,119 ​ $ 267,427 Sinosure Credit Facility, due 2027-2028, net of unamortized deferred finance costs of $1,706 and $1,884 ​ ​ 232,631 ​ ​ 244,243 8.5% Senior Notes, due 2023, net of unamortized deferred finance costs of $701 and $855 ​ ​ 24,299 ​ ​ 24,145 ​ ​ ​ 506,049 ​ ​ 535,815 Less current portion ​ ​ (61,483) ​ ​ (61,483) Long-term portion ​ $ 444,566 ​ $ 474,332

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	6 Months Ended
	Jun. 30, 2021
ACCUMULATED OTHER COMPREHENSIVE LOSS [Abstract]
Components of Accumulated Other Comprehensive Loss	The components of accumulated other comprehensive loss, net of related taxes, in the condensed consolidated balance sheets follow: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 December 31, 2020 Unrealized losses on derivative instruments ​ $ (14,276) ​ $ (24,098) Items not yet recognized as a component of net periodic benefit cost (pension plans) ​ ​ (8,641) ​ ​ (8,515) ​ ​ $ (22,917) ​ $ (32,613) ​ ​ The changes in the balances of each component of accumulated other comprehensive loss, net of related taxes, during the three and six months ended June 30, 2021 and 2020 follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Unrealized losses on cash flow hedges ​ Items not yet recognized as a component of net periodic benefit cost ​ Total Balance as of March 31, 2021 ​ $ (13,815) ​ $ (8,579) ​ $ (22,394) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ (3,431) ​ ​ (62) ​ ​ (3,493) Amounts reclassified from accumulated other comprehensive loss ​ ​ 2,970 ​ ​ — ​ ​ 2,970 Balance as of June 30, 2021 ​ $ (14,276) ​ $ (8,641) ​ $ (22,917) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of March 31, 2020 ​ $ (26,717) ​ $ (8,245) ​ $ (34,962) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ (2,828) ​ ​ 64 ​ ​ (2,764) Amounts reclassified from accumulated other comprehensive loss ​ ​ 1,645 ​ ​ — ​ ​ 1,645 Balance as of June 30, 2020 ​ $ (27,900) ​ $ (8,181) ​ $ (36,081) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Unrealized losses on cash flow hedges ​ Items not yet recognized as a component of net periodic benefit cost ​ Total Balance as of December 31, 2020 ​ $ (24,098) ​ $ (8,515) ​ $ (32,613) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ 3,849 ​ ​ (126) ​ ​ 3,723 Amounts reclassified from accumulated other comprehensive loss ​ ​ 5,973 ​ ​ — ​ ​ 5,973 Balance as of June 30, 2021 ​ $ (14,276) ​ $ (8,641) ​ $ (22,917) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of December 31, 2019 ​ $ (11,732) ​ $ (8,838) ​ $ (20,570) Current period change, excluding amounts reclassified ​ ​ ​ ​ ​ ​ ​ ​ ​ from accumulated other comprehensive loss ​ ​ (18,949) ​ ​ 657 ​ ​ (18,292) Amounts reclassified from accumulated other comprehensive loss ​ ​ 2,781 ​ ​ — ​ ​ 2,781 Balance as of June 30, 2020 ​ $ (27,900) ​ $ (8,181) ​ $ (36,081)
Reclassification Out of Accumulated Other Comprehensive Income (Loss)	​ Amounts reclassified out of each component of accumulated other comprehensive loss follow: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, ​ ​ (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 ​ Statement of Operations Reclassifications of losses on cash flow hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps entered into by the Company's ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity in income of equity method joint venture investees ​ $ 261 ​ $ 228 ​ $ 555 ​ $ 388 ​ affiliated companies Interest rate swaps entered into by the Company's subsidiaries ​ ​ 1,149 ​ ​ 1,417 ​ ​ 2,265 ​ ​ 2,312 ​ Interest expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reclassifications of losses on derivatives subsequent to ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ discontinuation of hedge accounting ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate collar entered into by the Company's subsidiaries ​ ​ — ​ ​ — ​ ​ — ​ ​ 81 ​ Interest expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reclassifications of losses on other-than-insignificant ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ financing element of derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps entered into by the Company's subsidiaries ​ ​ 1,560 ​ ​ — ​ ​ 3,153 ​ ​ — ​ Interest expense Total before and net of tax ​ $ 2,970 ​ $ 1,645 ​ $ 5,973 ​ $ 2,781 ​ ​ ​

REVENUE (Tables)

REVENUE (Tables)	6 Months Ended
	Jun. 30, 2021
REVENUE [Abstract]
Schedule of Disaggregated Revenue	The following table presents the Company’s revenues from leases accounted for under ASC 842 and revenues from services accounted for under ASC 606 for the three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Totals Three months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 15,245 ​ $ 11,210 ​ $ 26,455 Time and bareboat charter revenues ​ ​ 10,076 ​ ​ 1,638 ​ ​ 11,714 Voyage charter revenues from non-variable lease payments ​ ​ 787 ​ ​ 908 ​ ​ 1,695 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 6,440 ​ ​ — ​ ​ 6,440 Total shipping revenues ​ $ 32,548 ​ $ 13,756 ​ $ 46,304 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 72,446 ​ $ 27,613 ​ $ 100,059 Time and bareboat charter revenues ​ ​ 26,655 ​ ​ — ​ ​ 26,655 Voyage charter revenues from non-variable lease payments ​ ​ 2,690 ​ ​ 1,705 ​ ​ 4,395 Voyage charter revenues from variable lease payments ​ ​ 50 ​ ​ — ​ ​ 50 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 8,566 ​ ​ — ​ ​ 8,566 Total shipping revenues ​ $ 110,407 ​ $ 29,318 ​ $ 139,725 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Crude ​ Product ​ ​ ​ (Dollars in thousands) ​ Tankers ​ Carriers ​ Totals Six months ended June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 32,903 ​ $ 18,211 ​ $ 51,114 Time and bareboat charter revenues ​ ​ 23,154 ​ ​ 3,258 ​ ​ 26,412 Voyage charter revenues from non-variable lease payments (1) ​ ​ 1,727 ​ ​ 1,482 ​ ​ 3,209 Voyage charter revenues from variable lease payments ​ ​ — ​ ​ 51 ​ ​ 51 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 12,274 ​ ​ — ​ ​ 12,274 Total shipping revenues ​ $ 70,058 ​ $ 23,002 ​ $ 93,060 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues from leases ​ ​ ​ ​ ​ ​ ​ ​ ​ Pool revenues ​ $ 142,696 ​ $ 58,572 ​ $ 201,268 Time and bareboat charter revenues ​ ​ 35,259 ​ ​ — ​ ​ 35,259 Voyage charter revenues from non-variable lease payments ​ ​ 10,043 ​ ​ 2,406 ​ ​ 12,449 Voyage charter revenues from variable lease payments ​ ​ 1,170 ​ ​ — ​ ​ 1,170 Revenues from services ​ ​ ​ ​ ​ ​ ​ ​ ​ Voyage charter revenues from lightering services ​ ​ 14,916 ​ ​ — ​ ​ 14,916 Total shipping revenues ​ $ 204,084 ​ $ 60,978 ​ $ 265,062 (1) Includes $0.5 million of loss of hire proceeds received during the first quarter of 2021 .
Schedule of Contract Related Receivables, Assets and Liabilities with Customers	​ The following table provides information about receivables, contract assets and contract liabilities from contracts with customers, and significant changes in contract assets and liabilities balances, associated with revenue from services accounted for under ASC 606. Balances related to revenues from leases accounted for under ASC 842 are excluded from the table below. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Voyage receivables - Billed receivables ​ Contract assets (Unbilled voyage receivables) ​ Contract liabilities (Deferred revenues and off hires) Opening balance as of January 1, 2021 ​ $ 2,148 ​ $ 166 ​ $ — Closing balance as of June 30, 2021 ​ ​ 3,107 ​ ​ 125 ​ ​ — ​

LEASES (Tables)

LEASES (Tables)	6 Months Ended
	Jun. 30, 2021
Lease [Abstract]
Schedule of lease cost	The Company currently has two major categories of leases - chartered-in vessels and leased office and other space. The expenses recognized during the three and six months ended June 30, 2021 and 2020 for the lease component of these leases are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 ​ ​ 2021 ​ ​ 2020 Operating lease cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Charter hire expenses ​ $ 2,470 ​ $ 2,977 ​ $ 4,891 ​ $ 6,705 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Office and other space ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ General and administrative ​ ​ 274 ​ ​ 257 ​ ​ 547 ​ ​ 506 Voyage expenses ​ ​ 42 ​ ​ 42 ​ ​ 84 ​ ​ 84 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term lease cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vessel assets (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Charter hire expenses ​ ​ 1,055 ​ ​ 1,126 ​ ​ 1,956 ​ ​ 2,926 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Office and other space ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ General and administrative ​ ​ — ​ ​ — ​ ​ — ​ ​ 29 Total lease cost ​ $ 3,841 ​ $ 4,402 ​ $ 7,478 ​ $ 10,250 (1) Excludes vessels spot chartered-in under operating leases and employed in the Crude Tankers Lightering business for periods of less than one month each, totaling $0.1 million and $0.3 million for the three and six months ended June 30, 2021, respectively, compared with $0.1 million and $0.2 million for the three and six months ended June 30, 2020, respectively , including both lease and non-lease components.
Supplemental lease information	Supplemental cash flow information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, (Dollars in thousands) ​ ​ 2021 ​ ​ 2020 Cash paid for amounts included in the measurement of lease liabilities ​ ​ ​ ​ ​ ​ Operating cash flows used for operating leases ​ $ 5,522 ​ $ 7,295 ​ Supplemental balance sheet information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ June 30, 2021 ​ December 31, 2020 Operating lease right-of-use assets ​ $ 16,999 ​ $ 21,588 ​ ​ ​ ​ ​ ​ ​ Current portion of operating lease liabilities ​ $ (7,226) ​ $ (8,867) Long-term operating lease liabilities ​ ​ (7,541) ​ ​ (10,253) Total operating lease liabilities ​ $ (14,767) ​ $ (19,120) ​ ​ ​ ​ ​ ​ ​ Weighted average remaining lease term - operating leases ​ ​ 2.45 years ​ ​ 2.75 years Weighted average discount rate - operating leases ​ ​ 6.98% ​ ​ 7.21%
Schedule of lease maturity receivables	​ ​ The future minimum revenues, before reduction for brokerage commissions, expected to be received on non-cancelable time charters for five Panamaxes, one LR2, and one VLCC and the related revenue days as of June 30, 2021 are as follows: ​ ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Amount ​ Revenue Days 2021 ​ $ 11,706 ​ 499 2022 ​ ​ 16,425 ​ 365 2023 ​ ​ 3,195 ​ 71 Future minimum revenues ​ $ 31,326 ​ 935 ​
Office Space And Lightering Workboat Dock Space [Member]
Lease [Abstract]
Schedule of lease maturity payments	Payments of lease liabilities for office and other space as of June 30, 2021 are as follows: ​ ​ ​ ​ ​ (Dollars in thousands) ​ ​ Amount 2021 ​ $ 302 2022 ​ ​ 273 2023 ​ ​ 229 2024 ​ ​ 178 Total lease payments ​ ​ 982 less imputed interest ​ ​ (69) Total operating lease liabilities ​ $ 913 ​
Bareboat Charters-In [Member]
Lease [Abstract]
Schedule of lease maturity payments	Payments of lease liabilities and related number of operating days under these operating leases as of June 30, 2021 are as follows: ​ Bareboat Charters-in: ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Amount ​ Operating Days 2021 ​ $ 3,165 ​ 368 2022 ​ ​ 6,278 ​ 730 2023 ​ ​ 4,532 ​ 556 Total lease payments ​ ​ 13,975 ​ 1,654 less imputed interest ​ ​ (1,092) ​ ​ Total operating lease liabilities ​ $ 12,883 ​ ​ ​
Time Charters-In [Member]
Lease [Abstract]
Schedule of lease maturity payments	Time Charters-in: ​ ​ ​ ​ ​ ​ (Dollars in thousands) ​ Amount ​ Operating Days 2021 ​ $ 975 ​ 229 Total lease payments (lease component only) ​ ​ 975 ​ 229 less imputed interest ​ ​ (4) ​ ​ Total operating lease liabilities ​ $ 971 ​ ​ ​

BASIS OF PRESENTATION (Narrativ

BASIS OF PRESENTATION (Narrative) (Details)	Jul. 21, 2021property	Jul. 16, 2021USD ($)property	Jul. 01, 2021property	Jun. 30, 2021propertysegment
Property, Plant and Equipment [Line Items]
Number of reportable segments | segment				2
Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Number of vessels acquired | $		$ 64
Vessel/Fleet [Member]
Property, Plant and Equipment [Line Items]
Number of vessels in fleet				39
Vessel/Fleet [Member] | Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Number of vessels in fleet		97
Maritime Equipment Not Including New Builds [Member]
Property, Plant and Equipment [Line Items]
Number of vessels in fleet				36
Charter In Vessels [Member]
Property, Plant and Equipment [Line Items]
Number of vessels in fleet				3
Vessels with Interest In [Member]
Property, Plant and Equipment [Line Items]
Number of vessels in fleet				2
Very Large Crude Carrier [Member] | Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Number of vessels marketed to be sold			1
Medium Range Vessels To Be Disposed Of [Member]
Property, Plant and Equipment [Line Items]
Number of vessels marketed to be sold				6
Medium Range Vessels To Be Disposed Of [Member] | Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Number of vessels marketed to be sold	1		4
Maritime Equipment New Builds [Member]
Property, Plant and Equipment [Line Items]
Number of vessels in fleet				3

MERGER TRANSACTIONS (Details)

MERGER TRANSACTIONS (Details)	Jul. 16, 2021USD ($)shares	Jun. 30, 2021USD ($)shares	Jun. 30, 2020USD ($)	Jul. 15, 2021USD ($)	Dec. 31, 2020shares
Asset Acquisition [Line Items]
Expenditures for vessels and vessel improvements		$ 24,130,000	$ 40,949,000
Accelerated shares vested | shares	5,035
Common stock, shares, issued | shares		28,128,298			28,014,877
Common stock, shares, outstanding | shares		28,128,298			28,014,877
Subsequent Event [Member]
Asset Acquisition [Line Items]
Special dividends that can be paid prior to the effective date under the business combination				$ 31,500,000
Asset acquisition special dividends per share costs	$ 1.12
Accelerated shares vested | shares	5,035
Common stock, shares, issued | shares	50,674,393
Common stock, shares, outstanding | shares	50,674,393
Subsequent Event [Member] | Diamond S Shareholders [Member]
Asset Acquisition [Line Items]
Percentage of outstanding shares	44.25%
Subsequent Event [Member] | Pre Merger International Seaways Shareholders [Member]
Asset Acquisition [Line Items]
Percentage of outstanding shares	55.75%
Subsequent Event [Member] | Scenario, Forecast | Special Advisor [Member]
Asset Acquisition [Line Items]
Labor and related expense	$ 500,000
Subsequent Event [Member] | Financial Guarantee [Member] | Diamond S Shipping Inc | $360 Million Credit Agreement [Member]
Asset Acquisition [Line Items]
Credit facility, maximum borrowing capacity	360,000,000
Subsequent Event [Member] | Financial Guarantee [Member] | Diamond S Shipping Inc | $525 Million Credit Agreement [Member]
Asset Acquisition [Line Items]
Credit facility, maximum borrowing capacity	525,000,000
Subsequent Event [Member] | Restricted Stock [Member]
Asset Acquisition [Line Items]
Shares issued in asset acquisition	$ 72,994
Diamond S Shipping Inc
Asset Acquisition [Line Items]
Asset acquisition transaction cost accrued		$ 4,800,000
Expenditures for vessels and vessel improvements		$ 4,400,000
Diamond S Shipping Inc | Subsequent Event [Member]
Asset Acquisition [Line Items]
Asset acquisition conversion ratio of acquiree stock into acquirer stock	0.55375
Percentage of outstanding shares	44.25%
Common Stock [Member] | Diamond S Shipping Inc | Subsequent Event [Member]
Asset Acquisition [Line Items]
Shares issued in asset acquisition	$ 22,536,647

SIGNIFICANT ACCOUNTING POLICI_3

SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Summary Of Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents, noncurrent	$ 16,173		$ 16,173	$ 16,398	$ 16,287
Amortization of financing costs	500		1,000
Interest costs capitalized	58		$ 58
2017 Term Loan Facility, Sinosure Credit Facility, ABN Term Loan Facility, 8.5% Senior Notes and 10.75% Subordinated Notes [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization of financing costs		$ 700		$ 1,600
2020 Debt Facilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred finance costs, gross		7,300
Revenue, Product and Service Benchmark [Member] | Product Concentration Risk [Member] | Pool Revenue Leases [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage			94.00%		88.00%
Term Loan [Member] | 2017 Term Loan Facility, Sinosure Credit Facility, ABN Term Loan Facility, 8.5% Senior Notes and 10.75% Subordinated Notes [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred finance costs, gross	5,900		$ 5,900		$ 6,900
Term Loan [Member] | Core Revolving Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred finance costs, gross		$ 800
Revolving Credit Facility [Member] | Core Revolving Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred finance costs, gross	$ 700		$ 700		$ 800

SIGNIFICANT ACCOUNTING POLICI_4

SIGNIFICANT ACCOUNTING POLICIES (Activity for allowance for credit losses) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Balance Beginning	$ 55
Provision for expected credit losses	43
Write-offs charged against the allowance	(3)
Balance Ending	$ 95

EARNINGS PER COMMON SHARE (Narr

EARNINGS PER COMMON SHARE (Narrative) (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive awards	0	169,811	0	176,847
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Participating securities allocated a portion of income	61,437		56,291
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Participating securities allocated a portion of income		39,093		45,100
Potentially dilutive securities			272,922
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities			811,906
Antidilutive securities excluded from computation of earnings per share, amount	1,086,589	965,994	1,013,234	891,853

EARNINGS PER COMMON SHARE (Reco

EARNINGS PER COMMON SHARE (Reconciliation of Net Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
EARNINGS PER COMMON SHARE [Abstract]
Common Stockholders	$ (18,785)	$ 64,272	$ (32,154)	$ 97,227
Participating securities	2	86	6	150
Net (loss)/income	$ (18,783)	$ 64,358	$ (32,148)	$ 97,377

BUSINESS AND SEGMENT REPORTIN_2

BUSINESS AND SEGMENT REPORTING (Reportable Segments Information) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)property	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)segmentproperty	Jun. 30, 2020USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Revenues, services	$ 46,304	$ 139,725	$ 93,060	$ 265,062
Depreciation and amortization	17,079	18,880	33,833	37,147
Loss on disposal of vessels and other property	4,005	4,134	4,016	1,330
Adjusted (loss)/income from vessel operations	(6,101)	78,591	(9,754)	136,864
Equity in income/(loss) of affiliated companies	5,375	5,205	10,843	10,316
Investments in and advances to affiliated companies	149,580	155,191	149,580	155,191
Adjusted total assets	1,374,117	1,609,765	1,374,117	1,609,765
Expenditures for vessels and vessel improvements			24,130	40,949
Payments for drydocking			14,720	12,513
Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	44,718	135,289	89,887	255,020
International Crude Tankers Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	32,548	110,407	70,058	204,084
Depreciation and amortization	13,039	14,732	26,042	28,977
Loss on disposal of vessels and other property	4,005	4,134	4,016	1,330
Adjusted (loss)/income from vessel operations	(7,058)	62,883	(8,015)	106,824
Equity in income/(loss) of affiliated companies	5,375	5,205	10,843	10,316
Investments in and advances to affiliated companies	142,171	146,861	142,171	146,861
Adjusted total assets	$ 1,122,807	1,288,235	1,122,807	1,288,235
Expenditures for vessels and vessel improvements			22,359	22,451
Payments for drydocking			$ 7,992	12,121
International Crude Tankers Segment [Member] | Two Floating Storage and Offloading Vessels [Member]
Segment Reporting Information [Line Items]
Number of Vessels Operated by Joint Venture | property	2		2
International Crude Tankers Segment [Member] | Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	$ 31,096	105,890	$ 67,046	194,744
International Product Carriers Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	13,756	29,318	23,002	60,978
Depreciation and amortization	4,022	4,125	7,750	8,123
Loss on disposal of vessels and other property	0	0
Adjusted (loss)/income from vessel operations	975	15,731	(1,698)	30,087
Equity in income/(loss) of affiliated companies	0	0
Investments in and advances to affiliated companies	7,409	8,330	7,409	8,330
Adjusted total assets	251,310	321,530	251,310	321,530
Expenditures for vessels and vessel improvements			1,771	18,498
Payments for drydocking			6,728	392
International Product Carriers Segment [Member] | Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	13,622	29,399	22,841	60,276
Other Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	0	0
Depreciation and amortization	18	23	41	47
Loss on disposal of vessels and other property	0	0
Adjusted (loss)/income from vessel operations	(18)	(23)	(41)	(47)
Equity in income/(loss) of affiliated companies	0	0
Investments in and advances to affiliated companies	0	0	0	0
Adjusted total assets	0	0	$ 0	$ 0
Other Segment [Member] | Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	$ 0	$ 0

BUSINESS AND SEGMENT REPORTIN_3

BUSINESS AND SEGMENT REPORTING (Reconciliation of Time Charter Revenue to Shipping Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues, services	$ 46,304	$ 139,725	$ 93,060	$ 265,062
Add: Voyage expenses	1,586	4,436	3,173	10,042
Time Charter Equivalent Services [Member]
Revenues, services	$ 44,718	$ 135,289	$ 89,887	$ 255,020

BUSINESS AND SEGMENT REPORTIN_4

BUSINESS AND SEGMENT REPORTING (Reconciliation of Income/(Loss) from Vessel Operations to Loss Before Reorganization) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Total adjusted (loss)/income from vessel operations of all segments	$ (6,101)	$ 78,591	$ (9,754)	$ 136,864
General and administrative expenses	(6,829)	(6,694)	(14,969)	(14,128)
Provision for credit losses	(2)	129	(43)	67
Third-party debt modification fees	0	0	0	(232)
Merger and integration related costs	(481)		(481)	0
Loss on disposal of vessels and other property, including impairments	(4,005)	(4,134)	(4,016)	(1,330)
Consolidated income/(loss) from vessel operations	(17,418)	67,892	(29,263)	121,241
Equity in income/(loss) of affiliated companies	5,375	5,205	10,843	10,316
Other income/(expense)	267	143	559	(13,289)
Interest expense	(7,006)	(8,881)	(14,286)	(20,890)
(Loss)/income before income taxes	(18,782)	64,359	(32,147)	97,378
Vessel Operations [Member]
Total adjusted (loss)/income from vessel operations of all segments	(6,101)	78,591	(9,754)	136,864
General and administrative expenses	(6,829)	(6,694)	(14,969)	(14,128)
Provision for credit losses	(2)	129	(43)	67
Third-party debt modification fees	0	0	0	(232)
Merger and integration related costs	(481)		(481)	0
Loss on disposal of vessels and other property, including impairments	(4,005)	(4,134)	(4,016)	(1,330)
Consolidated income/(loss) from vessel operations	(17,418)	67,892	(29,263)	121,241
Equity in income/(loss) of affiliated companies	5,375	5,205	10,843	10,316
Other income/(expense)	267	143	559	(13,289)
Interest expense	(7,006)	(8,881)	(14,286)	(20,890)
(Loss)/income before income taxes	$ (18,782)	$ 64,359	$ (32,147)	$ 97,378

BUSINESS AND SEGMENT REPORTIN_5

BUSINESS AND SEGMENT REPORTING (Reconciliation of Assets of Segments to Consolidated Amounts) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Segment Reporting Information [Line Items]
Adjusted total assets	$ 1,374,117		$ 1,609,765
Cash and cash equivalents	117,391	$ 199,390	128,063
Restricted cash	16,173	16,287	16,398
Other unallocated amounts	11,184		4,730
Total assets	1,518,865	$ 1,586,539	1,758,956
Other Segment [Member]
Segment Reporting Information [Line Items]
Adjusted total assets	$ 0		$ 0

VESSELS (Narrative) (Details)

VESSELS (Narrative) (Details) $ in Thousands	Jul. 28, 2021property	Jul. 21, 2021property	Jul. 01, 2021property	Mar. 11, 2021USD ($)property	Jun. 30, 2021USD ($)	Jun. 30, 2021USD ($)property	Jun. 30, 2020USD ($)
Impairment of long-lived assets held-for-use						$ 3,497	$ 5,469
Proceeds from disposal of vessels and other property, net						3,431	$ 13,578
Interest costs capitalized					$ 58	58
Panamax 2003 Vessel To Be Disposed Of [Member]
Impairment of long-lived assets to be disposed of					3,500
Panamax 2003 Vessel To Be Disposed Of [Member] | Write Down Vessel Value To Fair Value [Member]
Impairment of long-lived assets to be disposed of					3,400
Panamax 2003 Vessel To Be Disposed Of [Member] | Estimated Costs To Sell Vessel [Member]
Impairment of long-lived assets to be disposed of					100
Dual Fuel LNG VLCC Under Construction [Member]
Remaining cost of construction of vessels					273,800	273,800
Number of vessels in construction | property				3
Accumulated expenditures related to property plant and equipment					$ 14,600	14,600
Interest costs capitalized						58
Leasing term of property				7 years
Dual Fuel LNG VLCC Under Construction [Member] | Scenario, Plan [Member]
Expected construction costs				$ 290,000
Two Panamaxes [Member]
Proceeds from nonrefundable deposit						$ 3,900
Medium Range Vessels To Be Disposed Of [Member]
Number of vessels marketed to be sold | property						6
Subsequent Event [Member] | Very Large Crude Carrier [Member]
Number of vessels marketed to be sold | property			1
Subsequent Event [Member] | Two Panamaxes [Member]
Number of vessels marketed to be sold | property	2
Subsequent Event [Member] | Medium Range Vessels To Be Disposed Of [Member]
Number of vessels marketed to be sold | property		1	4

EQUITY METHOD INVESTMENTS (Narr

EQUITY METHOD INVESTMENTS (Narrative) (Details) $ in Thousands	Mar. 29, 2018USD ($)	Apr. 30, 2018USD ($)	Jun. 30, 2021USD ($)contractitem	Dec. 31, 2020USD ($)
Schedule of Equity Method Investments [Line Items]
Number of joint ventures | item			2
Investments in and advances to affiliated companies			$ 149,580	$ 141,924
Other Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
Investments in and advances to affiliated companies			$ 13,100
FSO Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Number of contracts related to joint venture | contract			2
FSO Joint Venture [Member] | FSO Asia and FSO Africa [Member]
Schedule of Equity Method Investments [Line Items]
Investments in and advances to affiliated companies			$ 136,500
FSO Joint Venture [Member] | Two Floating Storage and Offloading Vessels [Member]
Schedule of Equity Method Investments [Line Items]
Number of contracts related to joint venture | contract			2
LNG Joint Venture, TI Africa and TI Asia Limited [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage			50.00%
FSO Term Loan [Member] | FSO Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Minimum liquidity level, threshold amount		$ 50,000
Minimum liquidity level, threshold percentage of debt		5.00%
Minimum cash, threshold amount, debt instrument covenant		$ 30,000
Guarantor obligations, maximum exposure, undiscounted			$ 33,200
Guarantor obligations, current carrying value			$ 3
Debt instrument, basis spread on variable rate			2.00%
Secured Debt [Member] | FSO Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Line of credit facility, maximum borrowing capacity	$ 220,000
Proceeds from long-term lines of credit	$ 220,000
Financial Guarantee [Member] | FSO Term Loan [Member] | FSO Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from long-term lines of credit		$ 110,000

EQUITY METHOD INVESTMENTS (Resu

EQUITY METHOD INVESTMENTS (Results of Operations of Equity Method Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Shipping revenues	$ 46,304	$ 139,725	$ 93,060	$ 265,062
(Loss)/income from vessel operations	(17,418)	67,892	(29,263)	121,241
Other income/(expense)	267	143	559	(13,289)
Interest expense	(7,006)	(8,881)	(14,286)	(20,890)
Income tax (provision)/benefit	(1)	(1)	(1)	(1)
Net (loss)/income	(18,783)	64,358	(32,148)	97,377
Equity Method Investments [Member]
Shipping revenues	26,109	26,119	51,954	52,143
Ship operating expenses	14,439	14,241	28,370	28,481
(Loss)/income from vessel operations	11,670	11,878	23,584	23,662
Other income/(expense)	(9)		(9)	40
Interest expense	(1,098)	(1,721)	(2,310)	(3,595)
Income tax (provision)/benefit	(981)	(944)	(1,973)	(1,867)
Net (loss)/income	$ 9,582	$ 9,213	$ 19,292	$ 18,240

VARIABLE INTEREST ENTITIES (V_3

VARIABLE INTEREST ENTITIES (VIEs) (Narrative) (Details) $ in Thousands	Jun. 30, 2021USD ($)item	Dec. 31, 2020USD ($)
Variable Interest Entity [Line Items]
Number of commercial pools	5
Number of joint ventures	2
Accounts receivable, net, current | $	$ 50,981	$ 43,362
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Number of commercial pools	1
Number of joint ventures	2
Variable Interest Entity, Not Primary Beneficiary [Member] | FSO Joint Venture [Member]
Variable Interest Entity [Line Items]
Accounts receivable, net, current | $	$ 14,900

VARIABLE INTEREST ENTITIES (V_4

VARIABLE INTEREST ENTITIES (VIEs)) (Balance Sheet Carrying Amounts Related to VIEs) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Jun. 30, 2020
Variable Interest Entity [Line Items]
Investments in Affiliated Companies	$ 149,580	$ 155,191
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments in Affiliated Companies	$ 140,603

VARIABLE INTEREST ENTITIES (V_5

VARIABLE INTEREST ENTITIES (VIEs) (Comparison of Liability to Maximum Exposure to Loss) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Other Liabilities	$ 13,410	$ 14,861
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Other Liabilities	3
Maximum Exposure to Loss	$ 173,853

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended			6 Months Ended
	Jul. 31, 2020	Jun. 30, 2020	Jan. 27, 2020	Jun. 30, 2021	Jun. 30, 2020	Apr. 30, 2020	Jan. 28, 2020
Fair Value Of Financial Instruments Derivatives And Fair Value Disclosures [Line Items]
Derivative, notional amount						$ 25,000
Derivative, fixed interest rate						0.50%
Extinguishment of debt				$ 0	$ 382,699
Change in fair value of interest rate collar recorded through earnings				$ 0	$ (1,271)
Interest Rate Cap/Collar [Member]
Fair Value Of Financial Instruments Derivatives And Fair Value Disclosures [Line Items]
Derivative, notional amount			$ 350,000
Change in fair value of interest rate collar recorded through earnings			$ 1,300
Interest Rate Swap [Member]
Fair Value Of Financial Instruments Derivatives And Fair Value Disclosures [Line Items]
Derivative, notional amount							$ 250,000
Derivative, fixed interest rate							1.97%
Average floor rate							0.00%
Sinosure Credit Facility [Member]
Fair Value Of Financial Instruments Derivatives And Fair Value Disclosures [Line Items]
Derivative, fixed interest rate	2.35%	2.76%			2.76%
Derivative, maturity date	Dec. 21, 2027	Mar. 21, 2025

FAIR VALUE OF FINANCIAL INSTR_4

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Other Than Derivatives) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 133,564	$ 215,677
Restricted cash	16,173	16,287	$ 16,398
Sinosure Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure	(234,337)	(25,697)
Term Loan [Member] | INSW Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure		(271,571)
Term Loan [Member] | ABN Term Loan Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure		$ (246,127)
Term Loan [Member] | Core Term Loan Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure	(252,619)
Senior Notes [Member] | 8.5% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes Payable, Fair Value Disclosure	$ (25,600)
Debt instrument, interest rate, stated percentage	8.50%	8.50%
Subordinated Debt [Member] | 8.5% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, interest rate, stated percentage	8.50%	8.50%
Subordinated Debt [Member] | 10.75% Subordinated Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, interest rate, stated percentage	10.75%
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 133,564	$ 215,677
Fair Value, Inputs, Level 1 [Member] | Sinosure Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure	0	(25,697)
Fair Value, Inputs, Level 1 [Member] | Term Loan [Member] | INSW Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] | Term Loan [Member] | ABN Term Loan Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] | Term Loan [Member] | Core Term Loan Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure	0
Fair Value, Inputs, Level 1 [Member] | Senior Notes [Member] | 8.5% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes Payable, Fair Value Disclosure	(25,600)
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Fair Value, Inputs, Level 2 [Member] | Sinosure Credit Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure	(234,337)	0
Fair Value, Inputs, Level 2 [Member] | Term Loan [Member] | INSW Facilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure		(271,571)
Fair Value, Inputs, Level 2 [Member] | Term Loan [Member] | ABN Term Loan Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure		$ (246,127)
Fair Value, Inputs, Level 2 [Member] | Term Loan [Member] | Core Term Loan Facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Payable, Fair Value Disclosure	(252,619)
Fair Value, Inputs, Level 2 [Member] | Senior Notes [Member] | 8.5% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes Payable, Fair Value Disclosure	$ 0

FAIR VALUE OF FINANCIAL INSTR_5

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Non Current Portion of Derivative Assets [Member]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	$ 6,526	$ 2,129
Current Portion of Derivative Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(3,950)	(4,121)
Non Current Portion of Derivative Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(3,782)	(6,155)
Accounts Payable, Accrued Liabilities And Other Current Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(2,907)	(2,979)
Other Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(12,628)	(14,051)
Interest Rate Swap [Member] | Non Current Portion of Derivative Assets [Member] | Hybrid Instrument [Member]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	0	0
Interest Rate Swap [Member] | Current Portion of Derivative Liabilities [Member] | Hybrid Instrument [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	0	0
Interest Rate Swap [Member] | Non Current Portion of Derivative Liabilities [Member] | Hybrid Instrument [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	0	0
Interest Rate Swap [Member] | Accounts Payable, Accrued Liabilities And Other Current Liabilities [Member] | Hybrid Instrument [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(2,907)	(2,979)
Interest Rate Swap [Member] | Other Liabilities [Member] | Hybrid Instrument [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(12,628)	(14,051)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Non Current Portion of Derivative Assets [Member]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	6,526	2,129
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Current Portion of Derivative Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(3,950)	(4,121)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Non Current Portion of Derivative Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	(3,782)	(6,155)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Accounts Payable, Accrued Liabilities And Other Current Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	0	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivative Instruments in Hedges, Liabilities, at Fair Value	$ 0	$ 0

FAIR VALUE OF FINANCIAL INSTR_6

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Effect of Cash Flow Hedging Relationships) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Designated as Hedging Instrument [Member]
Total other comprehensive loss	$ (3,431)	$ (2,828)	$ 3,849	$ (18,949)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Total other comprehensive loss	(2,981)	$ (2,828)	4,765	$ (18,949)
Hybrid Instrument [Member] | Interest Rate Swap [Member]
Total other comprehensive loss	$ (450)		$ (916)

FAIR VALUE OF FINANCIAL INSTR_7

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Effect of Cash Flow Hedging Relationships on Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Effective portion of gain/(loss) reclassified from accumulated other comprehensive loss	$ 2,970	$ 1,645	$ 5,973	$ 2,781
Interest Expense [Member]
Effective portion of gain/(loss) reclassified from accumulated other comprehensive loss	2,709	1,417	5,418	3,664
Interest Rate Cap/Collar [Member] | Cash Flow Hedging [Member] | Not Designated as Hedging Instrument [Member]
Effective portion of gain/(loss) reclassified from accumulated other comprehensive loss			0	1,352
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Effective portion of gain/(loss) reclassified from accumulated other comprehensive loss	1,149	$ 1,417	2,265	2,312
Hybrid Instrument [Member] | Interest Rate Swap [Member] | Interest Rate Cap/Collar [Member]
Effective portion of gain/(loss) reclassified from accumulated other comprehensive loss	$ 1,560		$ 3,153	$ 0

FAIR VALUE OF FINANCIAL INSTR_8

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Fair Values of Assets and Liabilities Measured on Recurring Basis) (Details) - Interest Rate Swap [Member] - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Inputs, Level 1 [Member]
Derivative Asset	$ 6,526	$ 2,129
Derivative liability	(7,732)	(10,276)
Fair Value, Inputs, Level 2 [Member]
Derivative Asset	6,526	2,129
Derivative liability	$ (7,732)	$ (10,276)

FAIR VALUE OF FINANCIAL INSTR_9

FAIR VALUE OF FINANCIAL INSTRUMENTS, DERIVATIVES AND FAIR VALUE DISCLOSURES (Fair Value of Items Measured on Nonrecurring Basis) (Details) $ in Thousands	Jul. 01, 2021property	Jun. 30, 2021USD ($)	Jun. 30, 2021USD ($)
International Crude Tankers Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for sale, fair value disclosure		$ 6,542	$ 6,542
Impairment			(3,497)
International Crude Tankers Segment [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for sale, fair value disclosure		6,542	$ 6,542
Panamax 2003 Vessel To Be Disposed Of [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment		(3,500)
Panamax 2003 Vessel To Be Disposed Of [Member] | International Crude Tankers Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment		(3,500)
Subsequent Event [Member] | Very Large Crude Carrier [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of vessels marketed to be sold | property	1
Write Down Vessel Value To Fair Value [Member] | Panamax 2003 Vessel To Be Disposed Of [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment		(3,400)
Estimated Costs To Sell Vessel [Member] | Panamax 2003 Vessel To Be Disposed Of [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment		$ (100)

DEBT (Narrative) (Details)

DEBT (Narrative) (Details)	Jun. 30, 2021	Dec. 31, 2020
Subordinated Debt [Member] | 10.75% Subordinated Notes [Member]
Debt instrument, interest rate, stated percentage	10.75%
Subordinated Debt [Member] | 8.5% Senior Notes [Member]
Debt instrument, interest rate, stated percentage	8.50%	8.50%
Senior Notes [Member] | 8.5% Senior Notes [Member]
Debt instrument, interest rate, stated percentage	8.50%	8.50%

DEBT (Schedule of Long-term Deb

DEBT (Schedule of Long-term Debt Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 506,049	$ 535,815
Less current portion	(61,483)	(61,483)
Long-term portion	444,566	474,332
Sinosure Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt	232,631	244,243
Unamortized discount and deferred finance costs	1,706	1,884
Term Loan [Member] | Core Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term debt	249,119	267,427
Unamortized discount and deferred finance costs	3,500	4,145
Senior Notes [Member] | 8.5% Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	24,299	24,145
Unamortized discount and deferred finance costs	$ 701	$ 855
Debt instrument, interest rate, stated percentage	8.50%	8.50%
Subordinated Debt [Member] | 8.5% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	8.50%	8.50%
Subordinated Debt [Member] | 10.75% Subordinated Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	10.75%

DEBT (Debt Covenants) (Narrativ

DEBT (Debt Covenants) (Narrative) (Details) $ in Millions	Jan. 28, 2020USD ($)	Jun. 30, 2021USD ($)property	Dec. 31, 2020	Jul. 31, 2020
Debt instrument, covenant compliance		The Company was in compliance with the financial and non-financial covenants under all of its debt facilities as of June 30, 2021.
Debt instrument interest expense coverage ratio				2.50
Debt instrument covenant limitation on total borrowings percentage of total assets		70.00%
Debt instrument covenant net worth		$ 600
Number of vessels used as collateral on debt | property		20
2020 Debt Facilities [Member]
Minimum liquidity level, threshold amount	$ 50
Minimum liquidity level, threshold percentage of debt	5.00%
Threshold leverage ratio	0.60%
2020 Debt Facilities [Member] | Period Thereafter June 30, 2020 [Member]
Threshold ratio of consolidated EBITDA to consolidated cash interest expense	2.50
Core Term Loan Facility and Core Revolving Facility [Member]
Debt Instrument Covenant, Fair Market Value of the Core Collateral Vessels, Threshold Percentage Of Outstanding Principal Amount	135.00%
Sinosure Credit Facility [Member]
Debt instrument covenant minimum security coverage percentage of aggregate loan principal		135.00%
Debt instrument maximum consolidated leverage ratio		0.60%
Debt instrument minimum consolidated liquidity unrestricted consolidated cash and cash equivalents		$ 25
Debt instrument minimum consolidated liquidity total consolidated cash and cash equivalents		$ 50
Debt instrument covenant percentage of total indebtedness		5.00%
Debt instrument property aggregate covenant		$ 9
Debt instrument per piece of property covenant		$ 1.5
Senior Notes [Member] | 8.5% Senior Notes [Member]
Debt instrument, interest rate, stated percentage		8.50%	8.50%
Subordinated Debt [Member] | 8.5% Senior Notes [Member]
Debt instrument, interest rate, stated percentage		8.50%	8.50%

DEBT (Interest Expense, Debt Mo

DEBT (Interest Expense, Debt Modification, Repurchases and Extinguishment) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Mar. 31, 2020
Debt Instrument [Line Items]
Interest Expense	$ 6,000		$ 10,200	$ 12,300	$ 17,300
Gain (Loss) on extinguishment of debt				0	(1,014)
Other income	267		143	559	(13,289)
(Gains) losses on repurchase and extinguishment of debt				13,500
Amortization of Issuance, Deferred Financing Costs, Commitments, Administrative and Other Fees for Debt Facilities [Member]
Debt Instrument [Line Items]
Interest Expense	6,900		8,700	14,100	20,600
2017 Term Loan, ABN Term Loan Facility and 10.75% Subordinated Notes [Member]
Debt Instrument [Line Items]
Write off of deferred debt issuance cost				12,500
2020 Debt Facilities [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross							$ 7,300
Core Term Loan Facility and Transition Term Loan Facility [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross							6,300
Payments of financing costs		$ 6,500
Core Term Loan Facility and Transition Term Loan Facility Deemed Expensed [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross			$ 200		$ 200
Revolving Credit Facility [Member] | Core Revolving Facility [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross	$ 700			$ 700		$ 800
Term Loan [Member] | Core Revolving Facility [Member]
Debt Instrument [Line Items]
Deferred finance costs, gross							$ 800
Senior Notes [Member] | 8.5% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	8.50%			8.50%		8.50%
Subordinated Debt [Member] | 10.75% Subordinated Notes [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee amount	$ 1,000			$ 1,000
Debt instrument, interest rate, stated percentage	10.75%			10.75%
Subordinated Debt [Member] | 8.5% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	8.50%			8.50%		8.50%

CAPITAL STOCK AND STOCK COMPE_2

CAPITAL STOCK AND STOCK COMPENSATION (Narrative) (Details)

Jul. 28, 2021$ / shares

Jul. 16, 2021USD ($)shares

Jun. 28, 2021USD ($)

Jun. 04, 2021$ / shares

Mar. 26, 2021USD ($)

Feb. 23, 2021$ / shares

Aug. 04, 2020USD ($)

Jun. 30, 2021$ / sharesshares

Jun. 30, 2020$ / sharesshares

Jun. 30, 2021USD ($)$ / sharesshares

Jun. 30, 2020USD ($)$ / sharesshares

Jul. 15, 2021USD ($)

Dec. 31, 2020shares

Oct. 28, 2020USD ($)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock repurchase program, authorized amount | $

$ 30,000,000

$ 50,000,000

Purchase of treasury stock | $

$ 0

$ 29,997,000

Dividends payable, date declared

Jun. 4, 2021

Feb. 23, 2021

Dividends payable, amount per share | $ / shares

$ 0.06

$ 0.06

Payments of dividends | $

$ 1,700,000

$ 1,700,000

$ 3,369,000

3,412,000

Dividends payable, date of record

Jun. 14, 2021

Mar. 11, 2021

Dividends payable, date to be paid

Sep. 23, 2021

Jun. 28, 2021

Mar. 26, 2021

Stock Repurchased and Retired During Period, Value | $

$ 30,000,000

Stock Repurchased and Retired During Period, Shares

1,417,292

Stock repurchased per share amount | $ / shares

$ 21.16

Stock repurchased during period, shares

0

Stock Repurchase Program Expiration Date

Aug. 4, 2022

Accelerated shares vested

5,035

Common stock, shares, issued

28,128,298

28,128,298

28,014,877

Common stock, shares, outstanding

28,128,298

28,128,298

28,014,877

Subsequent Event [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Dividends payable, date declared

Jul. 28, 2021

Dividends payable, amount per share | $ / shares

$ 0.06

Dividends payable, date of record

Sep. 9, 2021

Accelerated shares vested

5,035

Common stock, shares, issued

50,674,393

Common stock, shares, outstanding

50,674,393

Special dividends that can be paid prior to the effective date under the business combination | $

$ 31,500,000

Certain Employees and Senior Officers [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Granted, options

141,282

Grant date, value, per share

9.92

Grants, options, per share | $ / shares

$ 21.58

Fair value assumptions, risk free interest rate

1.06%

Fair value assumptions, expected dividend rate

1.23%

Fair value assumptions, expected volatility factor

0.55%

Fair value assumptions, expected life

6 years

Share based arrangement fair value method used

Black-Scholes option pricing model

Share based arrangement exercisable option period, maximum

90 days

Number of shares convertible into common shares per equity award represents

1

Restricted Stock Units (RSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Shares paid for tax withholding for share based compensation

28,145

23,744

50,975

56,954

Shares paid for tax withholding for share based compensation, per share amount | $ / shares

$ 19.23

$ 20.84

$ 20.21

$ 21.07

Number of shares convertible into common shares per equity award represents

1

Restricted Stock Units (RSUs) [Member] | Certain Employees and Senior Officers [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Granted

64,943

Granted, per share | $ / shares

$ 21.58

Restricted Stock [Member] | Subsequent Event [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Shares issued in asset acquisition | $

$ 72,994

Restricted Stock [Member] | Directors [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Granted

41,287

Granted, per share | $ / shares

$ 19.86

Share-based Compensation Award, Tranche One [Member] | Restricted Stock Units (RSUs) [Member] | Certain Employees and Senior Officers [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Granted, per share | $ / shares

$ 21.58

Vesting percentage

50.00%

Return on investment capital performance period

3 years

Share-based Payment Arrangement, Tranche Two [Member] | Restricted Stock Units (RSUs) [Member] | Certain Employees and Senior Officers [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Granted, per share | $ / shares

$ 22.50

Vesting percentage

1.00%

Total shareholder return performance period

3 years

Share-based Payment Arrangement, Tranche Three [Member] | Restricted Stock Units (RSUs) [Member] | Certain Employees and Senior Officers [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Total shareholder return peer group performance period

3 years

Diamond S Shipping Inc | Subsequent Event [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Asset acquisition conversion ratio of acquiree stock into acquirer stock

0.55375

Percentage of outstanding shares

44.25%

Diamond S Shipping Inc | Restricted Stock [Member] | Subsequent Event [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Nonvested Shares Outstanding

131,845

Diamond S Shipping Inc | Common Stock [Member] | Subsequent Event [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Shares issued in asset acquisition | $

$ 22,536,647

Diamond S Shareholders [Member] | Subsequent Event [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percentage of outstanding shares

44.25%

Pre Merger International Seaways Shareholders [Member] | Subsequent Event [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percentage of outstanding shares

55.75%

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
ACCUMULATED OTHER COMPREHENSIVE LOSS [Abstract]
Derivative instruments, gain (loss) reclassification from accumulated oci to income, estimated net amount to be transferred	$ 8.9

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE LOSS (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
ACCUMULATED OTHER COMPREHENSIVE LOSS [Abstract]
Unrealized losses on derivative instruments	$ (14,276)	$ (24,098)
Items not yet recognized as a component of net periodic benefit cost (pension plans)	(8,641)	(8,515)
Accumulated other comprehensive loss	$ (22,917)	$ (32,613)

ACCUMULATED OTHER COMPREHENSI_5

ACCUMULATED OTHER COMPREHENSIVE LOSS (Changes in Components of AOCI, Net of Related Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Balance, beginning	$ 967,763	$ 1,029,680	$ 972,042	$ 1,022,293
Other comprehensive (loss)/income, net of tax	(523)	(1,119)	9,696	(15,511)
Balance, ending	947,454	1,072,053	947,454	1,072,053
Accumulated Other Comprehensive Loss [Member]
Balance, beginning	(22,394)	(34,962)	(32,613)	(20,570)
Current period change, excluding amounts reclassified from accumulated other comprehensive loss	(3,493)	(2,764)	3,723	(18,292)
Amounts reclassified from accumulated other comprehensive loss	2,970	1,645	5,973	2,781
Other comprehensive (loss)/income, net of tax	(523)	(1,119)	9,696	(15,511)
Balance, ending	(22,917)	(36,081)	(22,917)	(36,081)
Unrealized losses on cash flow hedges [Member]
Balance, beginning	(13,815)	(26,717)	(24,098)	(11,732)
Current period change, excluding amounts reclassified from accumulated other comprehensive loss	(3,431)	(2,828)	3,849	(18,949)
Amounts reclassified from accumulated other comprehensive loss	2,970	1,645	5,973	2,781
Balance, ending	(14,276)	(27,900)	(14,276)	(27,900)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance, beginning	(8,579)	(8,245)	(8,515)	(8,838)
Current period change, excluding amounts reclassified from accumulated other comprehensive loss	(62)	64	(126)	657
Amounts reclassified from accumulated other comprehensive loss	0	0
Balance, ending	$ (8,641)	$ (8,181)	$ (8,641)	$ (8,181)

ACCUMULATED OTHER COMPREHENSI_6

ACCUMULATED OTHER COMPREHENSIVE LOSS (Amounts Reclassified out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Unrealized losses on available-for-sale securities:
Equity in income of affiliated companies	$ (18,782)	$ 64,359	$ (32,147)	$ 97,378
Income (loss) from equity method investments	5,375	5,205	10,843	10,316
Interest expense	7,006	8,881	14,286	20,890
Other income	267	143	559	(13,289)
Total reclassified out of AOCL, before tax	2,970	1,645	5,973	2,781
Interest Rate Cap/Collar [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Unrealized losses on available-for-sale securities:
Interest expense	0	0	0	81
Interest Rate Swap [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized losses on cash flow hedges [Member]
Unrealized losses on available-for-sale securities:
Equity in income of affiliated companies	261	228	555	388
Interest expense	1,149	$ 1,417	2,265	2,312
Hybrid Instrument [Member] | Interest Rate Swap [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Unrealized losses on available-for-sale securities:
Interest expense	$ 1,560		$ 3,153	$ 0

REVENUE (Narrative) (Details)

REVENUE (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)property	Jun. 30, 2020USD ($)
Revenues, Total | $	$ 46,304,000	$ 139,725,000	$ 93,060,000	$ 265,062,000
Contract with customer, performance obligation satisfied in previous period | $	0	$ 0	0	$ 15,000
Capitalized contract cost, gross | $	$ 0		$ 0
Lease cancellation period notice			90 days
Panamaxes [Member]
Number of vessels party to contracts | property			5
Very Large Crude Carrier [Member]
Number of vessels party to contracts | property			1
LR2 Vessel [Member]
Number of vessels party to contracts | property			1

REVENUE (Schedule of Disaggrega

REVENUE (Schedule of Disaggregated Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, non lease	$ 46,304		$ 139,725	$ 93,060	$ 265,062
Shipping revenues	46,304		139,725	93,060	265,062
Loss of hire proceeds		$ 500
International Crude Tankers Segment [Member]
Revenue, non lease	32,548		110,407	70,058	204,084
Shipping revenues	32,548		110,407	70,058	204,084
International Product Carriers Segment [Member]
Revenue, non lease	13,756		29,318	23,002	60,978
Shipping revenues	13,756		29,318	23,002	60,978
Other Segment [Member]
Revenue, non lease	0		0
Pool Revenue Leases [Member]
Shipping revenues	26,455		100,059	51,114	201,268
Pool Revenue Leases [Member] | Fixed-Price Contract [Member]
Revenue, operating leases	26,455		100,059	51,114	201,268
Pool Revenue Leases [Member] | International Crude Tankers Segment [Member] | Fixed-Price Contract [Member]
Revenue, operating leases	15,245		72,446	32,903	142,696
Pool Revenue Leases [Member] | International Product Carriers Segment [Member] | Fixed-Price Contract [Member]
Revenue, operating leases	11,210		27,613	18,211	58,572
Voyage Charter Leases Non Variable Payments [Member] | Fixed-Price Contract [Member]
Revenue, lease non-variable	1,695		4,395	3,209	12,449
Voyage Charter Leases Non Variable Payments [Member] | International Crude Tankers Segment [Member] | Fixed-Price Contract [Member]
Revenue, lease non-variable	787		2,690	1,727	10,043
Voyage Charter Leases Non Variable Payments [Member] | International Product Carriers Segment [Member] | Fixed-Price Contract [Member]
Revenue, lease non-variable	908		1,705	1,482	2,406
Voyage Charter Leases Variable Payments [Member] | Fixed-Price Contract [Member]
Revenue, operating leases			50	51	1,170
Voyage Charter Leases Variable Payments [Member] | International Crude Tankers Segment [Member] | Fixed-Price Contract [Member]
Revenue, operating leases			50		1,170
Voyage Charter Leases Variable Payments [Member] | International Product Carriers Segment [Member] | Fixed-Price Contract [Member]
Revenue, operating leases				51
Time and Bareboat Charter Leases [Member]
Shipping revenues	11,714		26,655	26,412	35,259
Time and Bareboat Charter Leases [Member] | Fixed-Price Contract [Member]
Revenue, operating leases	11,714		26,655	26,412	35,259
Time and Bareboat Charter Leases [Member] | International Crude Tankers Segment [Member] | Fixed-Price Contract [Member]
Revenue, operating leases	10,076		26,655	23,154	35,259
Time and Bareboat Charter Leases [Member] | International Product Carriers Segment [Member] | Fixed-Price Contract [Member]
Revenue, operating leases	1,638			3,258
Voyage Charter Leases [Member]
Shipping revenues	8,135		13,011	15,534	28,535
Voyage Charter Leases [Member] | Lightering Services Component [Member]
Revenue, non lease	6,440		8,566	12,274	14,916
Voyage Charter Leases [Member] | International Crude Tankers Segment [Member] | Lightering Services Component [Member]
Revenue, non lease	$ 6,440		$ 8,566	$ 12,274	$ 14,916

REVENUE (Schedule of Contract R

REVENUE (Schedule of Contract Related Receivables, Assets and Liabilities with Customers) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
REVENUE [Abstract]
Voyage receivables - receivables	$ 3,107	$ 2,148
Contract asset (voyage receivables unbilled receivables)	125	166
Contract liability (deferred revenues)	$ 0	$ 0

LEASES (Narrative) (Details)

LEASES (Narrative) (Details)	6 Months Ended
	Jun. 30, 2021propertylease
Leases [Line Items]
Number of major categories of leases | lease	2
Aframaxes [Member]
Leases [Line Items]
Vessels that have commitments to charter	2
LR1 Vessel [Member]
Leases [Line Items]
Number of vessels chartered	1
LR2 Vessel [Member]
Leases [Line Items]
Number of vessels chartered	1
Workboat Vessel [Member]
Leases [Line Items]
Vessels that have commitments to charter	1
Panamaxes [Member]
Leases [Line Items]
Number of vessels chartered	5
Bareboat Charters-In [Member] | Aframaxes [Member]
Leases [Line Items]
Number of vessels chartered	2
Time Charters-In [Member] | Very Large Crude Carrier [Member]
Leases [Line Items]
Number of vessels chartered	1
Maximum [Member]
Leases [Line Items]
Excluded vessels chartered period	1 month

LEASES (Schedule of lease cost)

LEASES (Schedule of lease cost) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating lease, cost	$ 5,863,000	$ 7,540,000	$ 11,604,000	$ 17,771,000
Total lease cost	3,841	4,402	7,478,000	10,250,000
Vessel/Fleet [Member] | Charter Hire Expense [Member]
Operating lease, cost	2,470	2,977	4,891,000	6,705,000
Short-term lease, cost	1,055	1,126	1,956,000	2,926,000
Office Space [Member] | General and Administrative Expense [Member]
Operating lease, cost	274	257	547,000	506,000
Short-term lease, cost			0	29,000
Office Space [Member] | Voyage Expense [Member]
Operating lease, cost	42	42	84,000	84,000
Lightering Services Component [Member] | Vessel/Fleet [Member]
Short-term lease, cost	$ 100,000	$ 100,000	$ 300,000	$ 200,000

LEASES (Supplemental lease info

LEASES (Supplemental lease information) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$ 5,522	$ 7,295
Operating Lease, Liability, Current	7,226		$ 8,867
Operating Lease, Liability, Noncurrent	7,541		10,253
Total operating lease liabilities	(14,767)		(19,120)
Operating Lease, Right-of-Use Asset	$ 16,999		$ 21,588
Operating Lease, Weighted Average Remaining Lease Term	2 years 5 months 12 days		2 years 9 months
Operating Lease, Weighted Average Discount Rate, Percent	6.98%		7.21%

LEASES (Bareboat and Time Chart

LEASES (Bareboat and Time Charters-In) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Leases [Line Items]
Total operating lease liabilities	$ 14,767	$ 19,120
Bareboat Charters-In [Member]
Leases [Line Items]
2021	3,165
2022	6,278
2023	4,532
Total lease payments	13,975
less imputed interest	(1,092)
Total operating lease liabilities	$ 12,883
2021, operating days	368 days
2022, operating days	730 days
2023, operating days	556 days
Operating days, total	1654 days
Time Charters-In [Member]
Leases [Line Items]
2021	$ 975
Total lease payments	975
less imputed interest	(4)
Total operating lease liabilities	$ 971
2021, operating days	229 days
Operating days, total	229 days

LEASES (Future Minimum Lease Ob

LEASES (Future Minimum Lease Obligations for Office Space) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Leases [Line Items]
Total operating lease liabilities	$ 14,767	$ 19,120
Office Space And Lightering Workboat Dock Space [Member]
Leases [Line Items]
2021	302
2022	273
2023	229
2024	178
Total lease payments	982
less imputed interest	(69)
Total operating lease liabilities	$ 913

LEASES (Future Minimum Revenues

LEASES (Future Minimum Revenues on Charters-Out) (Details) - Charters-Out [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Operating Leases, Future Minimum Payments Receivable [Abstract]
2021	$ 11,706
2022	16,425
2023	3,195
Net minimum lease payments	$ 31,326
2021, revenue days	499 days
2022, revenue days	365 days
2023, revenue days	71 days
Revenue Days	935 days

CONTINGENCIES (Narrative) (Deta

CONTINGENCIES (Narrative) (Details)	6 Months Ended
	Jun. 30, 2021USD ($)
Merchant Navy Officers Pension Fund [Member]
Loss Contingencies [Line Items]
Multiemployer plans deficit amount for entity	$ 0
Merchant Navy Ratings Pension Fund [Member]
Loss Contingencies [Line Items]
Multiemployer period of performance in the past	20 years