Share-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense	$ 14	[1]	$ 13	[1]	$ 46	[1]	$ 40	[1]
Unrecognized share-based compensation	$ 74				$ 74				$ 44

[1] Includes $3 million of expense recognized in merger integration-related costs for the six months ended June 30, 2014. Includes $3 million and $11 million of expense recognized in merger integration-related costs for the three and six months ended June 30, 2013, respectively.