Condensed Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ 42,345	$ (20,528)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	83,339	82,670
Amortization of debt discount	4,238	3,487
Amortization of debt issuance costs	2,703	5,238
Share-based compensation	7,569	7,613
Deferred income taxes	(5,716)	(3,019)
Equity in losses of investment	378	457
(Gain) loss on disposition of assets, net	(146)	39
Loss on extinguishment of long-term debt	1,183	397
Unrealized gain on derivative contracts, net	(2,289)	(4,291)
Changes in operating assets and liabilities:
Accounts receivable, net	(15,769)	(21,709)
Other current assets	(5,662)	(12,145)
Income tax payable	2,963	2,742
Accounts payable and accrued liabilities	6,968	30,675
Other non-current, net	28,723	(40,303)
Net cash provided by operating activities	150,827	31,323
Cash flows from investing activities:
Capital expenditures	(55,431)	(131,428)
Proceeds from sale of assets	25	10,000
Net cash used in investing activities	(55,406)	(121,428)
Cash flows from financing activities:
Issuance of Convertible Senior Notes due 2023	125,000	0
Repurchase of Convertible Senior Notes due 2032	(60,365)	0
Proceeds from term loan	0	100,000
Repayment of term loan	(62,872)	(193,508)
Repayment of Nordea Q5000 Loan	(26,786)	(26,786)
Repayment of MARAD Debt	(6,532)	(6,222)
Debt issuance costs	(3,867)	(3,694)
Net proceeds from issuance of common stock	0	219,504
Payments related to tax withholding for share-based compensation	(1,058)	(1,306)
Proceeds from issuance of ESPP shares	506	432
Net cash provided by (used in) financing activities	(35,974)	88,420
Effect of exchange rate changes on cash and cash equivalents	(947)	1,927
Net increase in cash and cash equivalents	58,500	242
Cash and cash equivalents:
Balance, beginning of year	266,592	356,647
Balance, end of period	$ 325,092	$ 356,889