CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - UNAUDITED - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 12,794	$ 9,403	$ 22,152	$ 19,094
Other comprehensive income, net of tax:
Foreign currency translation adjustments	7,923	3,171	(1,612)	4,075
Unrealized holding gains (losses) on short-term investments arising during period	3	(9)	6	10
Cash flow hedges:
Unrealized gains on change in fair value of interest rate swap contracts (net of tax effect of $0, $0, $0, and $110)				195
Reclassification adjustment for losses included in net income (net of tax effect of $0, $0, $0, and $(55))				(97)
Net change in cash flow hedges				98
Other comprehensive income (loss), net of tax	7,926	3,162	(1,606)	4,183
Total comprehensive income, net of tax	$ 20,720	$ 12,565	$ 20,546	$ 23,277