Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Granted (in Shares)	300,000
Granted	2 years 73 days
Stock Appreciation Rights (SARs) [Member]
Outstanding (in Shares)	2,000,000	[1],[2]	2,500,000
Per Share Weighted- Average Exercise Price	$ 24.59	[1],[2]	$ 20.39
Per Share Weighted- Average Grant Date Fair Value	$ 9.04	[1],[2]	$ 7.66
Weighted Average Remaining Contractual Term	4 years 36 days	[1],[2]	4 years
Vested and exercisable at December 31, 2012 (2) (in Shares)	800,000	[2]
Vested and exercisable at December 31, 2012 (2)	$ 18.74	[2]
Vested and exercisable at December 31, 2012 (2)	$ 7.14	[2]
Vested and exercisable at December 31, 2012 (2)	3 years 43 days	[2]
Granted (in Shares)	400,000
Granted	$ 37.81
Granted	$ 12.99
Granted	6 years 40 days
Forfeited	0 years
Forfeited (in Shares)
Forfeited
Forfeited
Exercised (in Shares)	(900,000)
Exercised	$ 18.35
Exercised	$ 6.82
Exercised	0 years

[1] At December 31, 2012, 1.2 million of these SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.

[2] At December 31, 2012, SARs outstanding had an intrinsic value of $42.9 million. SARs vested and exercisable had an intrinsic value of $23.1 million.