Stock-Based Compensation Plans (Employee Stock Purchase Plan And Authorized Preferred Stock And Preferred Stock Purchase Rights Plan) (Details) (USD $)			0 Months Ended	6 Months Ended				6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	May 10, 2011 Employee Stock Purchase Plan [Member]	Jun. 30, 2012 Employee Stock Purchase Plan [Member]	Jun. 30, 2012 Employee Stock Purchase Plan [Member] Maximum [Member]	Jun. 30, 2012 Authorized Preferred Stock And Preferred Stock Purchase Rights Plan [Member]	Jan. 21, 2004 Authorized Preferred Stock And Preferred Stock Purchase Rights Plan [Member]	Jun. 30, 2012 Authorized Preferred Stock And Preferred Stock Purchase Rights Plan [Member] Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee subscription rate					15.00%
Percentage of the lower of the market related to purchase of common stock				85.00%
Additional number of shares reserved for issuance			3,000,000
Shares of common stock reserved for future employee purchases				3,144,521
Shares issued during the period, in shares				535,617
Weighted average grant date fair value, in dollar per share				$ 22.79
Preferred stock, shares authorized	5,000,000	5,000,000
Number of shares reserved for issuance							750,000
Number of preferred shares declared for each share of common stock outstanding, in shares						1
Amount of Series A Participating Preferred Stock each right entitles its holder to purchase						.0001
Exercise price of Series A Participating Preferred Stock Rights, in dollar 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