Schedule of Derivative Instruments not Designated as Hedges Gains (Losses) (Detail) (Not Designated as Hedging Instrument, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income (Nonoperating Expense)	$ 61	$ 10	$ 30	$ 10