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	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gross amounts recognized, assets	$ 80	$ 72
Gross amounts offset, assets	(51)	(39)
Net amount presented in Consolidated Balance Sheet, assets	29	33
Gross amounts recognized, liabilities	83	84
Gross amounts offset, liabilities	(51)	(39)
Net amount presented in Consolidated Balance Sheet, liabilities	32	45
Aluminum Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gross amounts recognized, assets	49	40
Gross amounts offset, assets	(47)	(36)
Net amount presented in Consolidated Balance Sheet, assets	2	4
Gross amounts recognized, liabilities	79	81
Gross amounts offset, liabilities	(47)	(36)
Net amount presented in Consolidated Balance Sheet, liabilities	32	45
Interest Rate Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gross amounts recognized, assets	31	32
Gross amounts offset, assets	(4)	(3)
Net amount presented in Consolidated Balance Sheet, assets	27	29
Gross amounts recognized, liabilities	4	3
Gross amounts offset, liabilities	(4)	(3)
Net amount presented in Consolidated Balance Sheet, liabilities