CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - UNAUDITED - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 19,251	$ 14,014
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	3,847	7,710
Unrealized holding gains (losses) on short-term investments arising during period	18	(94)
Other comprehensive income, net of tax	3,865	7,616
Total comprehensive income, net of tax	$ 23,116	$ 21,630