Consolidated Statements of Comprehensive Income or Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (372,503)	$ (274,285)	$ 387,011
Derivative financial instruments:
Unrealized holding loss		(1,574)	(1,482)
Reclassification adjustment for (gain) loss included in net (loss) income	(5)	5,084	(2,379)
Investments in marketable securities:
Unrealized holding loss on investments	(6,559)	(4,940)	(69)
Reclassification adjustment for loss (gain) included in net (loss) income	11,600		(25)
Total other comprehensive gain (loss)	5,036	(1,430)	(3,955)
Comprehensive (loss) income	$ (367,467)	$ (275,715)	$ 383,056