Consolidated Statement of Changes in Stockholders' Equity - 9 months ended Sep. 30, 2016 - USD ($) $ in Thousands	Total	Common Stock Voting [Member]	Additional Paid-in Capital [Member]	Treasury Stock - Common Stock Voting [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2015	$ 390,713	$ 121	$ 321,215	$ (93,405)	$ 168,011	$ (5,229)
Net income	93,007				93,007
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(5,093)					(5,093)
Unrealized gain on securities available-for-sale, net of tax	177					177
Stock-based compensation	10,636		10,636
Exercise of stock options	2,172		2,172
Withholding tax payments on restricted stock vesting and stock option exercises	(5,929)	(1)	(5,928)
Excess tax benefits from stock-based compensation	9,166		9,166
Repurchases of common stock	(13,874)			(13,874)
Cash dividend on common stock	(29,275)				(29,275)
Ending Balance at Sep. 30, 2016	$ 451,700	$ 120	$ 337,261	$ (107,279)	$ 231,743	$ (10,145)