Share-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense	$ 18	[1]	$ 13	[1]	$ 44	[1]	$ 40	[1]
Unrecognized share-based compensation expense	$ 43				$ 43				$ 43

[1] Includes $0 and $7 million of expense recognized in integration-related costs for the three and nine months ended September 30, 2012, respectively. Includes $3 million and $12 million of expense recognized in integration-related costs for the three and nine months ended September 30, 2011, respectively.