Consolidated Statement of Changes in Stockholders' Equity - 6 months ended Jun. 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	62,089				62,089
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(4,041)					(4,041)
Unrealized gain on securities available-for-sale, net of tax	221					221
Stock-based compensation	6,937		6,937
Exercise of stock options	2,138		2,138
Withholding tax payments on restricted stock vesting and stock option exercises	(5,585)	(1)	(5,584)
Excess tax benefits from stock-based compensation	8,573		8,573
Repurchases of common stock	(5,400)			(5,400)
Cash dividend on common stock	(19,494)				(19,494)
Ending Balance at Jun. 30, 2016	$ 436,151	$ 120	$ 333,279	$ (98,805)	$ 210,606	$ (9,049)