Derivatives and Other Financial Instruments - Schedule of Reconciliation of Activity for Derivative Contracts (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Aluminum Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets, Beginning balance	$ 349
Fair value measurement, Assets, Sales
Fair value measurement, Assets, Cost of goods sold	(58)
Fair value measurement, Assets, Other expenses, net	(1)
Fair value measurement, Assets, Other comprehensive loss	9
Fair value measurement, Assets, Purchases, sales, issuances, and settlements
Fair value measurement, Assets, Transfers into and (or) out of Level 3
Fair value measurement, Assets, Foreign currency translation	27
Fair value measurement, Assets, Ending balance	326
Fair value measurement, Assets, Sales
Fair value measurement, Assets, Cost of goods sold
Fair value measurement, Assets, Other expenses, net	(1)
Fair value measurement, Liabilities, Beginning balance	410
Fair value measurement, Liabilities, Sales	(5)
Fair value measurement, Liabilities, Cost of goods sold
Fair value measurement, Liabilities, Other comprehensive loss	(21)
Fair value measurement, Liabilities, Purchases, sales, issuances, and settlements
Fair value measurement, Liabilities, Transfers into and (or) out of Level 3
Fair value measurement, Liabilities, Foreign currency translation
Fair value measurement, Liabilities, Ending balance	384
Fair value measurement, Liabilities, Sales
Fair value measurement, Liabilities, Cost of goods sold
Embedded Credit Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, Liabilities, Beginning balance	21
Fair value measurement, Liabilities, Cost of goods sold
Fair value measurement, Liabilities, Other income, net	(1)
Fair value measurement, Liabilities, Purchases, sales, issuances, and settlements
Fair value measurement, Liabilities, Transfers into and (or) out of Level 3
Fair value measurement, Liabilities, Foreign currency translation
Fair value measurement, Liabilities, Ending balance	20
Fair value measurement, Liabilities, Sales
Fair value measurement, Liabilities, Cost of goods sold
Fair value measurement, Liabilities, Other income, net	(1)
Energy Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value measurement, Assets, Beginning balance	6
Fair value measurement, Assets, Sales
Fair value measurement, Assets, Other comprehensive loss	5
Fair value measurement, Assets, Purchases, sales, issuances, and settlements
Fair value measurement, Assets, Transfers into and (or) out of Level 3
Fair value measurement, Assets, Ending balance	11
Fair value measurement, Assets, Sales
Fair value measurement, Assets, Cost of goods sold