Derivatives and Other Financial Instruments - Gross Amounts of Recognized Derivative Assets and Liabilities and Gross Amounts Offset in Accompanying Consolidated Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gross amounts recognized, assets	$ 72	$ 117
Gross amounts offset, assets	(39)	(72)
Net amount presented in Consolidated Balance Sheet, assets	33	45
Gross amounts recognized, liabilities	84	86
Gross amounts offset, liabilities	(39)	(72)
Net amount presented in Consolidated Balance Sheet, liabilities	45	14
Aluminum Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gross amounts recognized, assets	40	72
Gross amounts offset, assets	(36)	(55)
Net amount presented in Consolidated Balance Sheet, assets	4	17
Gross amounts recognized, liabilities	81	69
Gross amounts offset, liabilities	(36)	(55)
Net amount presented in Consolidated Balance Sheet, liabilities	45	14
Interest Rate Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gross amounts recognized, assets	32	45
Gross amounts offset, assets	(3)	(17)
Net amount presented in Consolidated Balance Sheet, assets	29	28
Gross amounts recognized, liabilities	3	17
Gross amounts offset, liabilities	$ (3)	$ (17)