Share-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense	$ 11	[1]	$ 14	[1]	$ 26	[1]	$ 27	[1]
Unrecognized share-based compensation expense	$ 47				$ 47				$ 43

[1] Includes $3 million and $7 million of expense recognized in integration-related costs for the three and six months ended June 30, 2012, respectively. Includes $6 million and $9 million of expense recognized in integration-related costs for the three and six months ended June 30, 2011, respectively.