Schedule I Condensed Financial Information Parent - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 165,994	$ 191,089	$ 193,978	$ 210,986
Restricted cash	58	7,272
Income taxes recoverable	1,122	877
Receivable from INSW	372	683
Total Current Assets	207,295	238,316
Restricted cash	217	8,572
Investments in subsidiaries	3,785	3,694
Other assets	23,150	18,658
Total Assets	931,887	1,030,497
Current Liabilities:
Accounts payable, accrued expenses and other current liabilities	34,220	57,222
Taxes payable, current	151	306
Total Current Liabilities	62,531	57,528
Reserve for uncertain tax positions	3,205	3,129
Long-term debt	420,776	525,082
Deferred income taxes	83,671	141,457
Total Liabilities	618,649	776,165
Equity:
Common stock - Class A ($0.01 par value; 166,666,666 shares authorized; 78,277,669 and 70,271,172 shares issued and outstanding)	783	702
Paid-in additional capital	584,675	583,526
Accumulated deficit	(265,758)	(321,736)
Stockholders Equity Subtotal	319,700	262,492
Accumulated other comprehensive loss	(6,462)	(8,160)
Total Equity	313,238	254,332	1,580,488	1,286,087
Total Liabilities and Equity	931,887	1,030,497
Parent Company [Member]
Current Assets:
Cash and cash equivalents	40,838	74,383	$ 15,395	$ 117,092
Restricted cash	58	7,272
Income taxes recoverable	113	199
Receivable from INSW	65	0
Prepaid expenses and other current assets	582	966
Total Current Assets	41,656	82,820
Restricted cash	217	8,572
Investments in subsidiaries	358,064	398,586
Intercompany receivables	3,279	809
Other assets	1	146
Receivable from INSW	0	47
Total Assets	403,217	490,980
Current Liabilities:
Accounts payable, accrued expenses and other current liabilities	2,013	10,324
Taxes payable, current	131	163
Total Current Liabilities	2,144	10,487
Reserve for uncertain tax positions	3,205	3,129
Long-term debt	685	80,896
Deferred income taxes	83,671	141,457
Intercompany payables	274	679
Total Liabilities	89,979	236,648
Equity:
Paid-in additional capital	584,675	583,526
Accumulated deficit	(265,758)	(321,736)
Stockholders Equity Subtotal	319,700	262,492
Accumulated other comprehensive loss	(6,462)	(8,160)
Total Equity	313,238	254,332
Total Liabilities and Equity	403,217	490,980
Parent Company [Member] | Common Class A [Member]
Equity:
Common stock - Class A ($0.01 par value; 166,666,666 shares authorized; 78,277,669 and 70,271,172 shares issued and outstanding)	$ 783	$ 702