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 income (loss)	$ 30,052	$ (81,445)	$ (376,980)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	108,745	114,187	120,401
Non-cash impairment charges	0	45,107	361,409
Amortization of debt discount	4,688	5,905	5,957
Amortization of debt issuance costs	6,154	7,733	5,664
Share-based compensation	10,877	5,862	6,543
Deferred income taxes	(54,585)	14,849	(103,022)
Equity in losses of investments	2,368	2,166	124,345
(Gain) loss on disposition of assets, net	39	(1,290)	(92)
Loss on early extinguishment of long-term debt	397	3,540	0
Unrealized (gains) losses and ineffectiveness on derivative contracts, net	(4,423)	(8,800)	18,281
Changes in operating assets and liabilities:
Accounts receivable, net	(28,424)	(22,437)	36,354
Other current assets	(15,680)	(2,386)	7,956
Income tax payable	3,949	(4,571)	(7,464)
Accounts payable and accrued liabilities	33,381	(630)	(63,817)
Other non-current, net	(45,900)	(39,076)	(24,730)
Net cash provided by operating activities	51,638	38,714	110,805
Cash flows from investing activities:
Capital expenditures	(231,127)	(186,487)	(320,311)
Distributions from equity investments	0	1,200	7,000
Proceeds from sale of equity investment	0	25,000	0
Proceeds from sale of assets	10,000	13,177	17,592
Net cash used in investing activities	(221,127)	(147,110)	(295,719)
Cash flows from financing activities:
Issuance of Convertible Senior Notes due 2022	0	125,000	0
Repurchase of Convertible Senior Notes due 2032	0	(138,401)	0
Proceeds from term loan	100,000	0	0
Repayment of term loan	(194,758)	(62,742)	(22,500)
Proceeds from Nordea Q5000 Loan	0	0	250,000
Repayment of Nordea Q5000 Loan	(35,715)	(35,714)	(17,857)
Repayment of MARAD Debt	(6,222)	(5,926)	(5,644)
Debt issuance costs	(3,717)	(4,655)	(1,737)
Net proceeds from issuance of common stock	219,504	96,547	0
Payments related to tax withholding for share-based compensation	(2,042)	(341)	(1,121)
Proceeds from issuance of ESPP shares	432	708	3,484
Net cash provided by (used in) financing activities	77,482	(25,524)	204,625
Effect of exchange rate changes on cash and cash equivalents	1,952	(3,625)	(2,011)
Net increase (decrease) in cash and cash equivalents	(90,055)	(137,545)	17,700
Cash and cash equivalents:
Balance, beginning of year	356,647	494,192	476,492
Balance, end of year	$ 266,592	$ 356,647	$ 494,192