Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (9,341)	$ 2,676	$ (20,863)	$ 4,986
Other comprehensive income:
Foreign currency translation adjustments net of zero tax	1,445	(1,750)	3,913	314
Unrealized gains on available-for-sale securities, net of zero tax	13	4	16	33
Total other comprehensive income (loss)	1,458	(1,746)	3,929	347
Comprehensive income (loss)	$ (7,883)	$ 930	$ (16,934)	$ 5,333