Share-Based Compensation Expense (Parenthetical) (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
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Expense recognized in integration-related costs	$ 0	$ 3	$ 7	$ 12