Summary of Changes in SARs Outstanding (Detail) (USD $)	6 Months Ended
	Jun. 30, 2011 Year
Weighted Average Remaining Contractual Term
Granted	1.5
Stock Appreciation Rights
SARs
Beginning Balance	2,500,000
Granted	400,000
Forfeited
Exercised	(300,000)
Ending Balance	2,600,000	[1],[2]
Vested and exercisable at June 30, 2011	1,200,000	[2]
Per Share Weighted Average Exercise Price
Beginning Balance	$ 17.22
Granted	$ 38.05
Forfeited
Exercised	$ 16.96
Ending Balance	$ 20.13	[1],[2]
Vested and exercisable at June 30, 2011	$ 17.71	[2]
Per Share Weighted Average Grant Date Fair Value
Beginning Balance	$ 6.62
Granted	$ 13.58
Forfeited
Exercised	$ 6.62
Ending Balance	$ 7.58	[1],[2]
Vested and exercisable at June 30, 2011	$ 6.67	[2]
Weighted Average Remaining Contractual Term
Beginning Balance	4.55
Granted	6.65
Forfeited
Exercised
Ending Balance	4.50	[1],[2]
Vested and exercisable at June 30, 2011	3.54	[2]

[1] Approximately 1.4 million of these outstanding SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.

[2] Total SARs outstanding had an intrinsic value of $52.0 million. SARs vested and exercisable had an intrinsic value of $27.1 million.