Consolidated Statements of Comprehensive Income or Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (274,285)	$ 387,011	$ 548,686
Derivative financial instruments:
Unrealized holding loss	(1,574)	(1,482)	(6,833)
Reclassification adjustment for loss (gain) included in net income	5,084	(2,379)	4,840
Investments in marketable securities:
Unrealized holding loss on investments	(4,940)	(69)	(6)
Reclassification adjustment for gain included in net income		(25)	(147)
Total other comprehensive (loss) income	(1,430)	(3,955)	(2,146)
Comprehensive (loss) income	$ (275,715)	$ 383,056	$ 546,540