CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total		Common stock	Additional Paid-in Captial	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury stock
Balance at Dec. 31, 2008	$ 436,316		$ 969	$ 116,621	$ 461,680	$ (10,825)	$ (132,129)
Balance (in shares) at Dec. 31, 2008			193,702				(13,046)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	14,303			14,303
Exercise of stock options	2,502		4	2,498
Exercise of stock options (in shares)			868
Excess tax benefits from share based payment arrangements	3,131			3,131
Repurchase of common stock	(86,173)						(86,173)
Repurchase of common stock (in shares)							(5,206)
Foreign currency translation	2,087					2,087
Change in unrealized loss on available-for-sale securities, net of tax	4,071					4,071
Net income	208,716				208,716
Balance at Dec. 31, 2009	584,953		973	136,553	670,396	(4,667)	(218,302)
Balance (in shares) at Dec. 31, 2009			194,570				(18,252)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	16,810			16,810
Exercise of stock options	20,824		15	20,809
Exercise of stock options (in shares)			2,892
Excess tax benefits from share based payment arrangements	12,374			12,374
Repurchase of common stock	(23,540)						(23,540)
Repurchase of common stock (in shares)							(1,250)
Foreign currency translation	1,837					1,837
Change in unrealized loss on available-for-sale securities, net of tax	3,111					3,111
Net income	212,029				212,029
Balance at Dec. 31, 2010	828,398	[1]	988	186,546	882,425	281	(241,842)
Balance (in shares) at Dec. 31, 2010			197,462				(19,502)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	18,619			18,619
Exercise of stock options	20,318		6	20,312
Exercise of stock options (in shares)			1,181
Issuance of restricted stock (in shares)			86
Excess tax benefits from share based payment arrangements	3,824			3,824
Repurchase of common stock	(176,392)						(176,392)
Repurchase of common stock (in shares)							(4,950)
Foreign currency translation	(3,306)					(3,306)
Change in unrealized loss on available-for-sale securities, net of tax	1,478					1,478
Net income	286,219				286,219
Balance at Dec. 31, 2011	$ 979,158	[1]	$ 994	$ 229,301	$ 1,168,644	$ (1,547)	$ (418,234)
Balance (in shares) at Dec. 31, 2011			198,729				(24,452)

[1] Stock Split - On January 11, 2012, the Company announced that its Board of Directors had approved a two-for-one stock split of its common stock to be effected in the form of a 100% stock dividend. The stock dividend was issued on February 15, 2012. See Note 1 for additional information.