Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 40,487	$ 38,023	$ 88,427	$ 80,486
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $1,328, $(1,106), $506 and $(1,634), respectively	(1,288)	1,325	(1,020)	960
Net unrealized gain (loss) on securities available-for-sale, net of tax of $18, $(20), $(89) and $(6), respectively	57	(33)	(277)	(10)
Comprehensive income	$ 39,256	$ 39,315	$ 87,130	$ 81,436