Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (7,710)	$ (10,874)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	5
Comprehensive loss	$ (7,705)	$ (10,874)