Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 148,089	$ 126,172	$ 96,037
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $(2,807), $5,407 and $(258), respectively	2,236	(7,037)	(512)
Net unrealized (loss) gain on securities available-for-sale, net of tax of $(39), $24, and $(111), respectively	(234)	38	(180)
Comprehensive income	$ 150,091	$ 119,173	$ 95,345