Derivatives and Other Financial Instruments - Schedule of Gain or Loss on Hedged Items and Derivative Contracts (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	$ 1	$ (62)	$ 128
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(19)	102	(103)
Aluminum Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(9)	(126)	38
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(9)	133	(41)
Interest Rate Contracts [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	10	64	90
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	$ (10)	$ (31)	$ (62)