Stockholders' Equity (Summary Of Stock Appreciation Rights Activity) (Details) (Stock Appreciation Rights [Member], USD $)	3 Months Ended
	Mar. 31, 2012
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested at December 31, 2011	262,800
Number of Rights, Granted	193,700
Number of Shares, Unvested at March 31, 2012	456,500
Weighted-Average Grant-Date Fair Value, Unvested at December 31, 2011	$ 48.79
Weighted Average Exercise Price, Granted	$ 46.39
Weighted-Average Grant-Date Fair Value, Unvested at March 31, 2012	$ 47.77
Weighted Average Remaining Contractual Term (in years), Outstanding at March 31, 2012	$ 9.72
Aggregate Intrinsic Value, Outstanding at March 31, 2012	$ 12.3	[1]
Closing stock price of common stock	$ 74.72

[1] The aggregate intrinsic value is calculated as the pre-tax difference between the exercise price of the underlying awards and the closing stock price per share of $74.72 of the Company's common stock on March 30, 2012. The amount is presented in millions.