Derivative and Other Financial Instruments - Schedule of Net Fair Values of Outstanding Derivative Contracts and Effect of Hypothetical Change (Increase or Decrease of 10%) in Market Prices or Rates (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	$ (102)
Index change of + / - 10%	47
Embedded Credit Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	(21)
Index change of + / - 10%	2
Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	6
Index change of + / - 10%	214
Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	(1)
Index change of + / - 10%	14
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	29
Index change of + / - 10%	$ 1