BUSINESS AND SEGMENT REPORTING (Reportable Segments Information) (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($) property	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) property segment	Jun. 30, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment			2
Revenues, services	$ 139,725	$ 69,010	$ 265,062	$ 170,884
Depreciation and amortization	18,880	18,818	37,147	37,747
Loss on disposal of vessels and other property, including impairments	4,134	1,548	1,330	1,500
Adjusted income/(loss) from vessel operations	78,591	(110)	136,864	27,267
Equity in income/(loss) of affiliated companies	5,205	8,015	10,316	16,085
Investments in and advances to affiliated companies	155,191	265,959	155,191	265,959
Adjusted total assets	1,609,765	1,710,148	1,609,765	1,710,148
Expenditures for vessels and vessel improvements			40,949	5,356
Payments for drydockings			12,513	10,878
Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	135,289	62,487	255,020	156,516
International Crude Tankers Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	110,407	52,130	204,084	132,515
Depreciation and amortization	14,732	14,795	28,977	29,272
Loss on disposal of vessels and other property, including impairments	4,134	(1)	1,330	16
Adjusted income/(loss) from vessel operations	62,883	(851)	106,824	22,511
Equity in income/(loss) of affiliated companies	5,205	4,603	10,316	9,373
Investments in and advances to affiliated companies	146,861	139,202	146,861	139,202
Adjusted total assets	$ 1,288,235	1,278,859	1,288,235	1,278,859
Expenditures for vessels and vessel improvements			22,451	5,339
Payments for drydockings			$ 12,121	9,612
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	$ 105,890	45,653	$ 194,744	118,239
International Product Carriers Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	29,318	16,880	60,978	38,369
Depreciation and amortization	4,125	3,994	8,123	8,412
Loss on disposal of vessels and other property, including impairments	0	1,549		1,484
Adjusted income/(loss) from vessel operations	15,731	781	30,087	4,839
Equity in income/(loss) of affiliated companies	0	0
Investments in and advances to affiliated companies	8,330	10,554	8,330	10,554
Adjusted total assets	321,530	315,086	321,530	315,086
Expenditures for vessels and vessel improvements			18,498	17
Payments for drydockings			392	1,266
International Product Carriers Segment [Member] \| Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	29,399	16,834	60,276	38,277
Other Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	0	0
Depreciation and amortization	23	29	47	63
Loss on disposal of vessels and other property, including impairments	0	0
Adjusted income/(loss) from vessel operations	(23)	(40)	(47)	(83)
Equity in income/(loss) of affiliated companies	0	3,412		6,712
Investments in and advances to affiliated companies	0	116,203	0	116,203
Adjusted total assets	$ 0	116,203	$ 0	$ 116,203
Other Segment [Member] \| Four LNG Carriers [Member]
Segment Reporting Information [Line Items]
Number of Vessels Operated by Joint Venture \| property	4		4
Other Segment [Member] \| Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	$ 0	$ 0

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Number of vessels operated by joint venture.

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Amounts paid for drydock costs performed pursuant to regulatory requirements.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

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