CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income / (loss)	$ 67,306	$ 129,569	$ (47,084)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Loss on disposal of vessels, net	24,169	805	8,729
Goodwill impairment	23,297	0	2,099
Goodwill write-off for sales of vessels	2,994		1,249
Loss on impairment of vessel held for sale		520
Payment-in-kind interest expense	17,776	5,220	7,354
Depreciation and amortization	87,191	47,572	46,118
Amortization of fair value of related-party chartered-in vessel	427	2,610
Amortization of deferred financing costs and senior notes	11,792	3,294	737
Write-off of commitment premium shares		6,040
Net unrealized gain on derivative financial instrument	(699)
Stock-based compensation expense	5,651	12,243	1,215
Provision for bad debts	(3,814)	3,764	1,990
Changes in assets and liabilities:
Decrease (increase) in due from charterers	15,377	32,633	(6,388)
Increase in due from Navig8 pools	(22,664)	(36,209)
Decrease in prepaid expenses and other current and noncurrent assets	53,094	18,880	10,960
Increase in working capital at Navig8 pools	(7,100)	(26,000)
Decrease in accounts payable and other current and noncurrent liabilities	(5,779)	(35,731)	(25,989)
Deferred drydock costs incurred	(10,086)	(9,321)	(12,787)
Net cash provided by (used in) operating activities	258,932	155,889	(11,797)
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for vessels under construction	(963,675)	(389,958)	(248,623)
Payment of professional fees for 2015 merger		(10,295)
Payment of capitalized interest	(16,881)	(20,016)	(6,629)
Proceeds from sale of vessels	86,897		22,703
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	(9,300)	(5,513)	(5,470)
Net cash used in investing activities	(902,959)	(398,858)	(238,019)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under credit facilities and senior notes	794,175	829,892	125,020
Repayments of credit facilities	(187,054)	(746,747)	(21,371)
Proceeds from issuance of common stock	26	236,351	197,743
Payment of underwriters' commission		(15,363)
Payment of common stock issuance costs		(6,543)	(1,621)
Deferred financing costs paid	(25,974)	(44,727)	(354)
Net cash provided by financing activities	581,173	252,863	299,417
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS		338	(5)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(62,854)	10,232	49,596
CASH AND CASH EQUIVALENTS, beginning of period	157,535	147,303	97,707
CASH AND CASH EQUIVALENTS, end of period	94,681	157,535	147,303
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION -
Cash paid during the period for interest, net of capitalized interest	$ 30,418	$ 9,240	$ 22,157