Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands	Total	Additional Paid-In Capital	Receivable for Common Stock Subscribed	Treasury Stock - Common Stock Voting	Accumulated Deficit	Accumulated Other Comprehensive Loss	Common Stock Voting	Common Stock Non-Voting
Balance at Dec. 31, 2009	$ 216,502	$ 313,896	$ (713)	$ (40,000)	$ (55,403)	$ (1,391)	$ 104	$ 9
Net income	31,428				31,428
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(564)					(564)
Unrealized net gain (loss) on securities available-for-sale, net of tax	304					304
Stock-based compensation	8,969	8,969
Exercise of stock options	6,761	6,757					4
Withholding tax payments on restricted stock vesting and stock option exercises	(2,055)	(2,055)
Tax benefit from the exercise of warrants in prior years	11,429	11,429
Excess tax benefits from stock-based compensation	1,619	1,619
Repayment of promissory notes	713		713
Purchase of treasury stock	(30,000)			(30,000)
Cash dividend on common stock and Series B Preferred Stock	(10,630)				(10,630)
Balance at Dec. 31, 2010	234,476	340,615		(70,000)	(34,605)	(1,651)	108	9
Net income	47,704				47,704
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(634)					(634)
Unrealized net gain (loss) on securities available-for-sale, net of tax	403					403
Stock-based compensation	6,859	6,859
Exercise of stock options	6,807	6,803					4
Withholding tax payments on restricted stock vesting and stock option exercises	(4,415)	(4,415)
Conversion of Series B Preferred stock to common stock voting	30,315	(20,688)		51,002			1
Tax benefit from the exercise of warrants in prior years	4,237	4,237
Excess tax benefits from stock-based compensation	7,305	7,305
Purchase of treasury stock	(6,935)			(6,935)
Cash dividend on common stock	(13,683)				(13,683)
Balance at Dec. 31, 2011	312,439	340,716		(25,933)	(584)	(1,882)	113	9
Net income	60,069				60,069
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(748)					(748)
Unrealized net gain (loss) on securities available-for-sale, net of tax	(463)					(463)
Stock-based compensation	8,385	8,385
Exercise of stock options	8,525	8,522					3
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		(15,878)		15,878			2	(2)
Repurchases of common stock	(75,133)	(52,908)		(22,218)				(7)
Cash dividend on common stock	(65,129)				(65,129)
Balance at Dec. 31, 2012	$ 242,717	$ 283,609		$ (32,273)	$ (5,644)	$ (3,093)	$ 118