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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	$ 21	$ (57)	$ 4	$ (125)
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(14)	61	(17)	129
Aluminum Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives	19	(59)	(1)	(130)
Amount of Gain or (Loss) Recognized in Earnings on Hedged Items	(12)	63	(12)	134
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)