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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	$ 23	$ 69	$ (102)	$ 17
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(5)	(74)	124	(38)
Aluminum Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	20	66	(110)	9
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(2)	(71)	132	(30)
Interest Rate Contracts [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	3	3	8	8
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	$ (3)	$ (3)	$ (8)	$ (8)