Share-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified				12 Months Ended
	Dec. 31, 2011 Year	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Stock Option Plan Effective until February 2007	Dec. 31, 2011 Performance based Vesting Condition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Option plan, terms				10 years
Stock Option plan, vesting period				vest after three years
Shares available for future grants under the long-term incentive plan	14,900,000
Weighted-average fair value of options at grant date	$ 17.02	$ 17.81	$ 8.89
Closing common stock price	$ 43.26
Aggregate intrinsic value of stock options outstanding	$ 64
Weighted-average remaining term of stock options outstanding (in years)	5.0
Aggregate intrinsic value of stock options exercisable	37
Weighted-average remaining term of stock options exercisable (in years)	4.1
Total compensation cost not yet recognized, restricted stock awards, weighted-average period (in years)	1.1
Total compensation cost not yet recognized, restricted stock awards	$ 25				$ 12
Total compensation cost not yet recognized, restricted stock awards, shares					666,000