Consolidated Statement of Changes in Stockholders' Equity - 3 months ended Mar. 31, 2017 - 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, 2016	$ 468,013	$ 120	$ 342,311	$ (117,330)	$ 255,140	$ (12,228)
Net income	42,463				42,463
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(365)					(365)
Unrealized net gain on securities available-for-sale, net of tax	23					23
Stock-based compensation	3,943		3,943
Exercise of stock options	500	1	499
Withholding tax payments on restricted stock vesting and stock option exercises	(7,642)		(7,642)
Repurchases of common stock	(12,207)			(12,207)
Cumulative effect of change in accounting for employee share-based payments	28		80		(52)
Cash dividend on common stock	(12,401)				(12,401)
Ending Balance at Mar. 31, 2017	$ 482,355	$ 121	$ 339,191	$ (129,537)	$ 285,150	$ (12,570)