Stockholders' Equity (Details) (USD $)	12 Months Ended			0 Months Ended	6 Months Ended	12 Months Ended			12 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	May 21, 2013 2012 Stock Repurchase Program [Member]	May 21, 2013 2012 Stock Repurchase Program [Member]	Dec. 31, 2013 2012 Stock Repurchase Program [Member]	Dec. 31, 2013 2010 Employee Stock Purchase Plan [Member]	Jun. 30, 2010 2010 Employee Stock Purchase Plan [Member]	Dec. 31, 2013 Incentive Stock Option [Member]	Dec. 31, 2013 Incentive Stock Option [Member] 1998 Plan [Member]	Dec. 31, 2013 Incentive Stock Option [Member] 2000 Plan [Member]	Dec. 31, 2013 Incentive Stock Option [Member] 2009 Plan [Member]	Dec. 31, 2013 Incentive Stock Option [Member] Amended 2009 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	54,484,760	55,948,924
Common stock, shares outstanding	54,484,760	55,948,942
Common stock, par value	$ 0.001	$ 0.001
Preferred Stock, Shares Authorized	5,000,000	5,000,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Preferred stock, par value	$ 0.001	$ 0.001
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 5.12	$ 8.20	$ 6.47
Dividend yield	0.00%	0.00%	0.00%
Expected life (in years)	5 years	5 years	5 years
Shares of common stock available for issuance							693,000	1,000,000		5,850,000	10,000,000	14,600,000	23,817,744
Increase in number of shares of common stock available for issuance											4,150,000	6,000,000	4,250,000
Stock option term													10 years
Unrecognized compensation cost related to nonvested share-based compensation arrangements									$ 30,100,000
Weighted average recognition period of unrecognized compensation cost									2 years
Proceeds from Stock Options Exercised	2,500,000	16,300,000	17,200,000
Total intrinsic value of options exercisable	26,200,000	20,800,000	21,900,000
Total intrinsic value of nonvested options	17,000,000	10,100,000	19,800,000
Total intrinsic value of all outstanding options	43,200,000	30,900,000	41,700,000
Stock Repurchase Program, Authorized Amount				30,000,000	20,000,000
Stock Repurchased During Period, Shares		0				2,391,362
Stock Repurchase Program, Remaining Authorized Repurchase Amount						$ 3,300,000