CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 66,130	$ 61,364	$ 62,882
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(14,203)	16,479	(18,925)
Unrealized holding gains (losses) on short-term investments arising during period	90	71	(62)
Other comprehensive income (loss), net of tax	(14,113)	16,550	(18,987)
Total comprehensive income, net of tax	$ 52,017	$ 77,914	$ 43,895