CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 62,882	$ 62,567	$ 35,711
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(18,925)	(12,902)	(15,060)
Unrealized holding gains (losses) on short-term investments arising during period	(62)	(103)	(35)
Cash flow hedges:
Unrealized gains on change in fair value of interest rate swap contracts (net of tax effect of $0, $0, and $110)			195
Reclassification adjustment for losses included in net income (net of tax effect of $0, $0, and $(55))			(97)
Net change in cash flow hedges			98
Other comprehensive loss, net of tax	(18,987)	(13,005)	(14,997)
Total comprehensive income, net of tax	$ 43,895	$ 49,562	$ 20,714