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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	$ (57)	$ (91)	$ (125)	$ (52)
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	61	87	129	36
Aluminum Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	(59)	(93)	(130)	(57)
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	63	89	134	41
Interest Rate Contracts [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	2	2	5	5
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	$ (2)	$ (2)	$ (5)	$ (5)