Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ 28,598	$ 30,052	$ (81,445)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	110,522	108,745	114,187
Non-cash goodwill impairment	0	0	45,107
Amortization of debt discounts	5,735	4,688	5,905
Amortization of debt issuance costs	3,592	6,154	7,733
Share-based compensation	9,925	10,877	5,862
Deferred income taxes	(2,430)	(54,585)	14,849
Equity in losses of investment	3,918	2,368	2,166
(Gain) loss on disposition of assets, net	(146)	39	(1,290)
Loss on extinguishment of long-term debt	1,183	397	3,540
Unrealized (gains) losses and ineffectiveness on derivative contracts, net	(2,324)	(4,423)	(8,800)
Changes in operating assets and liabilities:
Accounts receivable, net	20,920	(28,424)	(22,437)
Other current assets	(9,904)	(15,680)	(2,386)
Income tax payable	964	3,949	(4,571)
Accounts payable and accrued liabilities	(352)	33,381	(630)
Other non-current, net	26,543	(45,900)	(39,076)
Net cash provided by operating activities	196,744	51,638	38,714
Cash flows from investing activities:
Capital expenditures	(137,083)	(231,127)	(186,487)
Distributions from equity investment	0	0	1,200
Proceeds from sale of equity investment	0	0	25,000
Proceeds from sale of assets	25	10,000	13,177
Other	1,044	0	0
Net cash used in investing activities	(136,014)	(221,127)	(147,110)
Cash flows from financing activities:
Issuance of convertible senior notes	125,000	0	125,000
Repurchase of convertible senior notes	(60,365)	0	(138,401)
Proceeds from term loan	0	100,000	0
Repayment of term loans	(63,807)	(194,758)	(62,742)
Repayment of Nordea Q5000 Loan	(35,714)	(35,715)	(35,714)
Repayment of MARAD Debt	(6,532)	(6,222)	(5,926)
Debt issuance costs	(3,867)	(3,717)	(4,655)
Net proceeds from issuance of common stock	0	219,504	96,547
Payments related to tax withholding for share-based compensation	(1,407)	(2,042)	(341)
Proceeds from issuance of ESPP shares	506	432	708
Net cash provided by (used in) financing activities	(46,186)	77,482	(25,524)
Effect of exchange rate changes on cash and cash equivalents	(1,677)	1,952	(3,625)
Net increase (decrease) in cash and cash equivalents	12,867	(90,055)	(137,545)
Cash and cash equivalents:
Balance, beginning of year	266,592	356,647	494,192
Balance, end of year	$ 279,459	$ 266,592	$ 356,647