CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) / income	$ (168,541)	$ 67,306	$ 129,569
Adjustments to reconcile net (loss) / income to net cash provided by operating activities:
Loss on disposal of vessels, net	139,836	24,169	805
Goodwill impairment		23,297
Goodwill write-off for sales of vessels		2,994
Loss on impairment of vessels held for sale			520
Payment-in-kind interest expense	19,735	17,776	5,220
Depreciation and amortization	103,951	87,191	47,572
Amortization of fair value of related-party chartered-in vessel		427	2,610
Amortization of deferred financing costs and senior notes	15,311	11,792	3,294
Loss on litigation	400		6,040
Net unrealized loss (gain) on derivative financial instrument	14,046	(699)
Stock-based compensation expense	4,205	5,651	12,243
Provision for bad debts	1,013	(3,814)	3,764
Changes in assets and liabilities:
(Increase) decrease in due from charterers	(177)	15,377	32,633
Decrease (increase) in due from Navig8 pools	34,497	(22,664)	(36,209)
Decrease in prepaid expenses and other current and noncurrent assets	2,998	53,094	18,880
Decrease (increase) in working capital at Navig8 pools	7,000	(7,100)	(26,000)
Decrease in accounts payable and other current and noncurrent liabilities	(2,304)	(5,779)	(35,731)
Deferred drydock costs incurred	(17,434)	(10,086)	(9,321)
Net cash provided by operating activities	154,536	258,932	155,889
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for vessels under construction	(127,293)	(963,675)	(389,958)
Payment of professional fees for 2015 merger			(10,295)
Payment of capitalized interest	(1,892)	(16,881)	(20,016)
Proceeds from sale of vessels, net	331,661	86,897
Cash at Navig8 Crude upon merger			28,876
Deposit of cash merger consideration			(1,187)
Restricted cash			(765)
Purchase of vessel improvements and other fixed assets	(9,388)	(9,300)	(5,513)
Net cash provided by (used in) investing activities	193,088	(902,959)	(398,858)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under credit facilities	148,131	794,175	829,892
Repayments of credit facilities	(387,991)	(187,054)	(746,747)
Proceeds from issuance of common stock		26	236,351
Payment of underwriters' commission			(15,363)
Payment of common stock issuance costs			(6,543)
Deferred financing costs paid	(1,944)	(25,974)	(44,727)
Net cash (used in) provided by financing activities	(241,804)	581,173	252,863
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS			338
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	105,820	(62,854)	10,232
CASH AND CASH EQUIVALENTS, beginning of period	94,681	157,535	147,303
CASH AND CASH EQUIVALENTS, end of period	200,501	94,681	157,535
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION -
Cash paid during the period for interest, net of capitalized interest	$ 49,504	$ 30,418	$ 9,240