Stockholders' Equity (Summary Of Stock Appreciation Rights Activity) (Detail) (Stock Appreciation Rights [Member], USD $)	12 Months Ended
	Dec. 31, 2012
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding at December 31, 2011	525,600
Number of Shares, Granted	387,400
Number of Shares, Forfeited	(29,400)
Number of Shares, Outstanding at December 31, 2012	883,600
Number of Shares, Vested and exercisable at December 31, 2012	131,400
Weighted Average Exercise Price, Outstanding at December 31, 2011	$ 24.40
Weighted Average Exercise Price, Granted	$ 23.20
Weighted Average Exercise Price, Forfeited	$ 23.20
Weighted Average Exercise Price, Outstanding at December 31, 2012	$ 23.91
Weighted Average Exercise Price, Vested and exercisable at December 31, 2012	$ 24.40
Weighted Average Remaining Contractual Term (in years), Outstanding at December 31, 2012	8 years 11 months 19 days
Weighted Average Remaining Contractual Term (in years), Vested and exercisable at December 31, 2012	8 years 11 months 12 days
Aggregate Intrinsic Value, Outstanding at December 31, 2012	$ 24.1	[1]
Aggregate Intrinsic Value, Vested and exercisable at December 31, 2012	$ 3.5	[1]
Closing stock price of common stock	$ 51.16

[1] The aggregate intrinsic value is calculated as the pre-tax difference between the weighted-average exercise price of the underlying awards and the closing price per share of $51.16 of the Company's common stock on December 31, 2012. The amount is presented in millions.