Derivatives and Other Financial Instruments - Schedule of Gain or Loss on Hedged Items and Derivative Contracts (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain recognized in earnings related to the ineffective portion of hedging relationships	$ 1	$ 9
Aluminum contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain recognized in earnings related to the ineffective portion of hedging relationships	$ 12