BUSINESS AND SEGMENT REPORTING (Reportable Segments Information) (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	2
Revenues, services	$ 125,337	$ 101,874
Depreciation and amortization	18,267	18,929
Loss/(gain) on disposal of vessels and other property	(2,804)	(48)
Adjusted income/(loss) from vessel operations	58,273	27,377
Equity in income/(loss) of affiliated companies	5,111	8,070
Investments in and advances to affiliated companies	151,400	267,518
Adjusted total assets	1,624,925	1,748,545
Expenditures for vessels and vessel improvements	28,914	2,962
Payments for drydockings	7,565	4,438
Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	119,731	94,029
International Crude Tankers Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	93,677	80,385
Depreciation and amortization	14,245	14,477
Loss/(gain) on disposal of vessels and other property	(2,804)	17
Adjusted income/(loss) from vessel operations	43,949	23,362
Equity in income/(loss) of affiliated companies	5,111	4,770
Investments in and advances to affiliated companies	143,403	139,832
Adjusted total assets	1,292,689	1,306,866
Expenditures for vessels and vessel improvements	11,301	2,955
Payments for drydockings	7,205	4,231
International Crude Tankers Segment [Member] \| Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	88,854	72,586
International Product Carriers Segment [Member]
Segment Reporting Information [Line Items]
Revenues, services	31,660	21,489
Depreciation and amortization	3,998	4,418
Loss/(gain) on disposal of vessels and other property		(65)
Adjusted income/(loss) from vessel operations	14,353	4,058
Investments in and advances to affiliated companies	7,997	12,703
Adjusted total assets	332,236	326,696
Expenditures for vessels and vessel improvements	17,613	7
Payments for drydockings	360	207
International Product Carriers Segment [Member] \| Time Charter Equivalent Services [Member]
Segment Reporting Information [Line Items]
Revenues, services	30,877	21,443
Other Segments [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	24	34
Adjusted income/(loss) from vessel operations	$ (29)	(43)
Equity in income/(loss) of affiliated companies		3,300
Investments in and advances to affiliated companies		114,983
Adjusted total assets		$ 114,983

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This excludes items that are not allocated to a specific segment for segment reporting purposes, such as general and administrative overhead expense.

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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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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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The net cash outflow or inflow from purchases, sales and disposals of property, plant and equipment and other productive assets, including intangibles.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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