Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands	Total	Common Stock Voting [Member]	Additional Paid-in Capital [Member]	Treasury Stock - Common Stock Voting [Member]	Retained Earnings (Deficit) [Member]	Accumulated Other Comprehensive Loss [Member]	Common Stock Non-Voting [Member]
Beginning Balance at Dec. 31, 2011	$ 312,439	$ 113	$ 340,716	$ (25,933)	$ (584)	$ (1,882)	$ 9
Net income	60,069				60,069
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(748)					(748)
Unrealized net (loss) on securities available-for-sale, net of tax	(463)					(463)
Stock-based compensation	8,385		8,385
Exercise of stock options	8,525	3	8,522
Withholding tax payments on restricted stock vesting and stock option exercises	(20,003)		(20,003)
Excess tax benefits from stock-based compensation	14,775		14,775
Conversion of common stock non-voting to common stock voting		2	(15,878)	15,878			(2)
Repurchases of common stock	(75,133)		(52,908)	(22,218)			(7)
Cash dividend on common stock	(65,129)				(65,129)
Ending Balance at Dec. 31, 2012	242,717	118	283,609	(32,273)	(5,644)	(3,093)
Net income	76,016				76,016
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(537)					(537)
Unrealized net (loss) on securities available-for-sale, net of tax	(453)					(453)
Stock-based compensation	8,879		8,879
Exercise of stock options	3,039	1	3,038
Withholding tax payments on restricted stock vesting and stock option exercises	(5,001)		(5,001)
Excess tax benefits from stock-based compensation	5,032		5,032
Cash dividend on common stock	(19,330)				(19,330)
Ending Balance at Dec. 31, 2013	310,362	119	295,557	(32,273)	51,042	(4,083)
Net income	74,806				74,806
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(399)					(399)
Unrealized net (loss) on securities available-for-sale, net of tax	(55)					(55)
Stock-based compensation	9,769		9,769
Exercise of stock options	2,511	1	2,510
Withholding tax payments on restricted stock vesting and stock option exercises	(5,020)		(5,020)
Excess tax benefits from stock-based compensation	4,243		4,243
Repurchases of common stock	(37,974)			(37,974)
Cash dividend on common stock	(24,035)				(24,035)
Ending Balance at Dec. 31, 2014	$ 334,208	$ 120	$ 307,059	$ (70,247)	$ 101,813	$ (4,537)