Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 38,594	$ 34,130	$ 127,021	$ 114,616
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $240, $(953), $746 and $(2,586), respectively	(582)	1,102	(1,602)	2,061
Net unrealized gain (loss) on securities available-for-sale, net of tax of $23, $16, $(66) and $10, respectively	72	26	(205)	17
Comprehensive income	$ 38,084	$ 35,258	$ 125,214	$ 116,694