CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - UNAUDITED - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 10,837	$ 12,794	$ 32,341	$ 22,152
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(7,938)	7,923	(9,040)	(1,612)
Unrealized holding gains (losses) on short-term investments arising during period	(254)	3	657	6
Other comprehensive income (loss), net of tax	(8,192)	7,926	(8,383)	(1,606)
Total comprehensive income, net of tax	$ 2,645	$ 20,720	$ 23,958	$ 20,546