Share-Based Compensation Expense (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Expense (benefit) recognized in integration-related costs	$ (2)	$ 0	$ 9	$ 7