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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in earnings related to the ineffective portion of hedging relationships	$ 0	$ 1	$ 0	$ 10
Sales [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in earnings related to the ineffective portion of hedging relationships	$ 4	$ 4	$ 4	$ 16