Derivatives and Other Financial Instruments - Schedule of Gain or Loss on Hedged Items and Derivative Contracts (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
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	$ 69	$ (95)	$ 17	$ (20)
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(74)	97	(38)	51
Aluminum Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	66	(100)	9	(78)
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(71)	102	(30)	76
Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	3	5	8	58
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	$ (3)	$ (5)	$ (8)	$ (25)