Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net cash provided by operating activities	$ 119,866,000	$ 108,835,000
Cash flows from investing activities:
Capital expenditures	(168,172,000)	(156,802,000)
Purchases of marketable securities	0	(19,414,000)
Sales and maturities of marketable securities	17,901,000	146,265,000
Net cash used in investing activities	(150,271,000)	(29,951,000)
Cash flows from financing activities:
Borrowings under the Credit Facility	22,207,000	129,431,000
Payment of deferred financing fees	(1,533,000)	(8,158,000)
Restricted cash deposits	(22,126,000)	(11,094,000)
Proceeds from exercise of stock options	1,572,000	80,000
Tax payment upon settlement of stock awards	(1,753,000)	(586,000)
Net cash provided by (used in) financing activities	(5,492,000)	101,955,000
Effect of exchange rate changes on cash and cash equivalents	(71,000)	477,000
Net increase (decrease) in cash and cash equivalents	(35,968,000)	181,316,000
Cash and cash equivalents, beginning of period	371,167,000	185,665,000
Cash and cash equivalents, end of period	335,199,000	366,981,000
Supplemental cash flow information:
Interest paid	42,458,000	10,985,000
Income taxes paid, net	1,312,000	735,000
Supplemental disclosure of non-cash investing activities:
Property and equipment received but not paid for yet	152,722,000	5,388,000
Interest capitalized but not paid	14,272,000	13,314,000
Capitalized amortization of deferred financing costs	10,600,000	9,156,000
Capitalized paid-in-kind interest	253,000	25,136,000
Capitalized stock-based compensation	1,561,000	1,304,000
Series A Preferred Stock [Member]
Cash flows from financing activities:
Payment of Preferred Stock dividends	(1,750,000)	(3,500,000)
Supplemental disclosure of non-cash financing activities:
Dividends Payable	292,000	292,000
Series B Preferred Stock [Member]
Cash flows from financing activities:
Payment of Preferred Stock dividends	(2,109,000)	(4,218,000)
Supplemental disclosure of non-cash financing activities:
Dividends Payable	$ 352,000	$ 352,000