Derivatives and Other Financial Instruments - Schedule of Gains and Losses on Derivative Excluded from Assessment of Effectiveness Recognized in Current Earnings (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	$ (1)	$ 2
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	34	(121)	(138)
Amount of Gain or (Loss) Recognized in OCI on Derivatives (Effective Portion)	(12)	63	(21)
Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivatives (Effective Portion)	(10)	72	(6)
Aluminum Contracts [Member] | Other (Income) Expenses, Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	(1)	2
Aluminum Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	36	(114)	(106)
Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivatives (Effective Portion)		(3)	(10)
Energy Contracts [Member] | Cost of Goods Sold [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)		(8)	(25)
Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivatives (Effective Portion)		1	(3)
Foreign Exchange Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)		4	(6)
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivatives (Effective Portion)		(2)	(1)
Interest Rate Contracts [Member] | Other (Income) Expenses, Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)		(3)
Amount of Gain or (Loss) Recognized in OCI on Derivatives (Effective Portion)	(2)	(5)	(1)
Interest Rate Contracts [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Earnings (Effective Portion)	$ (2)		$ (1)