Income Taxes - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Net deferred tax assets	$ 3,700,000,000	$ 3,300,000,000
Period in which amount of our unrecognized tax benefits changes	12 months
Unrecognized tax benefits	76,000,000	96,000,000
Accruals for payment of interest and penalties	$ 55,000,000	$ 88,000,000