CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY/(DEFICIT) - USD ($)	Total	Common Class A [Member]	Common Class And Class B [Member]	Common Class B [Member]	Common Stock [Member]	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class And Class B [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Common Class A [Member]	Additional Paid-in Capital [Member] Common Class And Class B [Member]	Retained Earnings / (Accumulated Deficit) [Member]	Retained Earnings / (Accumulated Deficit) [Member] Common Class B [Member]	Accumulated Other Comprehensive Loss [Member]
Balance at Dec. 31, 2014	$ 1,286,087,000				$ 3,158,000			$ 1,507,334,000			$ (141,025,000)		$ (83,380,000)
Net income/(loss)	283,960,000										283,960,000
Other comprehensive income (loss)	9,919,000												9,919,000
Stock dividends declared	0				338,000			143,879,000			(144,217,000)
Issuance and vesting of restricted stock awards	0				5,000			(5,000)
Forfeitures and cancellation of restricted stock awards	(257,000)							(257,000)
Compensation related to Class A options granted, net of forfeitures		$ 621,000							$ 621,000
Amortization of restricted stock awards	1,217,000							1,217,000
Compensation related to Class A restricted stock awards		2,574,000							2,574,000
Repurchase of Class A warrants	(3,633,000)							(3,633,000)
Conversion of Class A and Class B warrants to common stock			$ 0				$ 219,000			$ (219,000)
Balance at Dec. 31, 2015	1,580,488,000				3,720,000			1,651,511,000			(1,282,000)		(73,461,000)
Net income/(loss)	(293,614,000)										(293,614,000)
Other comprehensive income (loss)	6,956,000												6,956,000
Issuance and vesting of restricted stock awards	0				3,000			(3,000)
Forfeitures and cancellation of restricted stock awards	(363,000)							(363,000)
Compensation related to Class A options granted, net of forfeitures		2,414,000							2,414,000
Conversion of Class A and Class B warrants to common stock			$ 0				$ 413,000			$ (413,000)
Stock dividends declared and paid	(30,573,000)			$ (1,337,000)				(5,070,000)			(25,503,000)	$ (1,337,000)
Vesting of restricted stock awards to be settled in cash	(528,000)							(528,000)
Compensation related to Class A restricted stock awards, net of forfeitures		5,882,000							5,882,000
Repurchase of Class A warrants and Class A common stock	(119,343,000)	(1,301,000)			(5,000)			(119,338,000)
Reverse stock split	0				(3,429,000)			(3,429,000)
Distribution of INSW stock	(895,650,000)							(953,995,000)					58,345,000
Balance at Dec. 31, 2016	254,332,000				702,000			583,526,000			(321,736,000)		(8,160,000)
Net income/(loss)	55,978,000										55,978,000
Other comprehensive income (loss)	1,698,000												1,698,000
Issuance and vesting of restricted stock awards	(1,000)				5,000			(6,000)
Forfeitures and cancellation of restricted stock awards	(1,157,000)							(1,157,000)
Compensation related to Class A options granted, net of forfeitures		281,000							281,000
Compensation related to Class A restricted stock awards		2,107,000							2,107,000
Conversion of Class A and Class B warrants to common stock		$ 0				$ 76,000			$ (76,000)
Balance at Dec. 31, 2017	$ 313,238,000				$ 783,000			$ 584,675,000			$ (265,758,000)		$ (6,462,000)