Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (198,471)	$ (117,732)	$ (53,504)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	5	(261)	(71)
Comprehensive loss	$ (198,466)	$ (117,993)	$ (53,575)