Stockholders’ Equity And Stock-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended				12 Months Ended									12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Apr. 21, 2010	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2004 Stock Options [Member]	Dec. 31, 1997 Stock Options [Member]	May 09, 1994 Stock Options [Member]	May 10, 2005 Restricted Stock [Member] Incentive Plan (2005) [Member]	Dec. 31, 2012 Restricted Stock [Member] Incentive Plan (2010) [Member]	May 11, 2010 Restricted Stock [Member] Incentive Plan (2010) [Member]	Dec. 31, 2012 Employee Stock Purchase Plan [Member]	Dec. 31, 2012 Authorized Preferred Stock And Preferred Stock Purchase Rights Plan [Member] item	Jan. 21, 2004 Authorized Preferred Stock And Preferred Stock Purchase Rights Plan [Member]	Dec. 31, 2012 Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved for issuance										13,668,750	4,050,000		3,362,304			750,000
Additional number of shares reserved for issuance (1997) (in shares)									10,631,250
Additional number of shares reserved for issuance (2004) (in shares)								1,125,000
Additional number of shares reserved for issuance (2010) (in shares)													3,000,000
Aggregate intrinsic value of stock options	$ 2,400,000	$ 13,000,000	$ 12,000,000
Unrecognized stock-based compensation expense					72,600												89,300,000
Unrecognized stock-based compensation expense, shares					18,600												3,805,274
Unrecognized stock-based compensation expense, weighted average fair value					$ 11.79												$ 24.62
Weighted average period for which unrecognized stock-based compensation expense recognized					1 year 2 months 12 days												7 years 4 months 24 days
Weighted average remaining contractual life of options exercisable	1 year 2 months 12 days
Aggregate intrinsic value of options outstanding	$ 7,800,000				$ 7,600,000
Options granted					0	0	0
Number of shares available for grant												3,871,389
Percentage of the lower of the market price related to purchase of common stock														85.00%
Maximum employee subscription rate														15.00%
Shares of common stock reserved for future employee purchases														2,557,655
Number of shares issued during the period														1,122,483
Weighted average grant date fair value, in dollar per share														$ 21.84
Preferred stock, shares authorized	5,000,000	5,000,000													5,000,000
Number of preferred shares declared for each share of common stock outstanding, in shares															1
Portion of a share of Series A Participating Preferred Stock each Right entitles its holder to purchase															one-thousandth
Exercise price of Series A Participating Preferred Stock Rights, in dollars per share															$ 200
Percentage of common stock before rights become exercisable															20.00%
Multiple of original exercise price for which holder is entitled to purchase (in number of times: 2x, 3x, etc.)															2
Redemption price of Series A Participating Preferred Stock															$ 0.01
Expiration date															May 10, 2014
Common stock repurchased	0	0	2,089,098
Weighted average prices of common stock repurchased			$ 20.04
Authorized common stock available for repurchase	3,932,245
Common stock authorized repurchased				1,011,147
Increased aggregate number of common stock authorized to repurchase under new share repurchase program				4,500,000