Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Preferred Stock [Member]	Common Stock [Member] USD ($)	Treasury Shares [Member] USD ($)	Additional Paid-in Capital [Member] USD ($)	Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Retained Earnings [Member] USD ($)	Total USD ($)
Balance, value at Dec. 31, 2010		$ 156		$ 717,375	$ (258)	$ 173,862	$ 891,135
Balance, shares at Dec. 31, 2010		78,141,000
Exercise of common stock options, shares		399,000
Exercise of common stock options, value		1		2,857			2,858
Employee stock purchase plan, shares		21,000
Employee stock purchase plan, value				194			194
Share-based compensation, shares
Share-based compensation, value				7,163			7,163
Unrealized gains on available for sale securities, net					48		48
Cumulative translation adjustment, net					951		951
Repurchase of shares, shares		(2,668,000)	2,668,000				2.7
Repurchase of shares, value			(50,000)				(50,000)
Stock option tax benefits				1,027			1,027
Net income						59,242	59,242
Balance, value at Jun. 30, 2011		$ 157	$ (50,000)	$ 728,616	$ 741	$ 233,104	$ 912,618
Balance, shares at Jun. 30, 2011		75,893,000