Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (31,897)	$ (46,312)	$ (96,571)	$ (210,054)
Other comprehensive income, net of income taxes:
Net unrealized gain (loss) on available-for-sale securities	(241)	0	405	0
Reclassification of net realized gains on available-for-sale securities included in net loss	(48)	0	(78)	0
Total other comprehensive income (loss)	(289)	0	327	0
Comprehensive loss	$ (32,186)	$ (46,312)	$ (96,244)	$ (210,054)