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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in earnings related to the ineffective portion of hedging relationships	$ (5)	$ 0	$ 0	$ 0
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	$ 1	$ 18	$ (12)	$ 22