CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]
Stockholders' Equity at Dec. 31, 2008	$ 526,076	$ 147	$ 521,613	$ 978	$ 3,338
Shares, Outstanding at Dec. 31, 2008		147,356
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under plans (shares)		5,923
Issuance of common stock under plans (value)	20,350	6	20,344
Stock-based compensation	14,608		14,608
Excess tax benefit from share based compensation	125		125
Accumulated other comprehensive loss	(242)			(242)
Net income	16,245				16,245
Stockholders' Equity at Dec. 31, 2009	577,162	153	556,690	736	19,583
Shares, Outstanding at Dec. 31, 2009		153,279
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under plans (shares)		8,184
Issuance of common stock under plans (value)	45,310	8	45,302
Stock-based compensation	17,800		17,800
Excess tax benefit from share based compensation	3,166		3,166
Accumulated other comprehensive loss	(256)			(256)
Net income	190,837				190,837
Stockholders' Equity at Dec. 31, 2010	834,019	161	622,958	480	210,420
Shares, Outstanding at Dec. 31, 2010		161,463
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under plans (shares)		4,662
Issuance of common stock under plans (value)	29,205	5	29,200
Stock-based compensation	25,786		25,786
Excess tax benefit from share based compensation	468		468
Accumulated other comprehensive loss	(340)			(340)
Net income	48,150				48,150
Stockholders' Equity at Dec. 31, 2011	$ 937,288	$ 166	$ 678,412	$ 140	$ 258,570
Shares, Outstanding at Dec. 31, 2011		166,125