Share-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense	$ 23	[1]	$ 32	[1]	$ 69	[1]	$ 72	[1]
Unrecognized share-based compensation	$ 62				$ 62				$ 44

[1] Includes $3 million of expense recognized in merger integration-related costs for the nine months ended September 30, 2014. Includes $(2) million and $9 million of (benefit) expense recognized in merger integration-related costs for the three and nine months ended September 30, 2013, respectively.