Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 18,799	$ 25,494	$ (25,546)
Unrealized gains (losses) on available-for-sale securities, net of tax	28	(8)	3
Comprehensive income (loss)	$ 18,827	$ 25,486	$ (25,543)