Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 34,130	$ 30,918	$ 114,616	$ 93,007
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $(953), $346, $(2,586) and $4,448, respectively	1,102	(1,052)	2,061	(5,093)
Net unrealized gain (loss) on securities available-for-sale, net of tax of $16, $(27), $10 and $109, respectively	26	(44)	17	177
Comprehensive income	$ 35,258	$ 29,822	$ 116,694	$ 88,091