Derivatives and Other Financial Instruments - Schedule of Reconciliation of Activity for Derivative Contracts (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Aluminum Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of year	$ 547	$ 10
Fair value measurement, Assets, Sales	(5)	(8)
Fair value measurement, Assets, Cost of goods sold	(202)	(107)
Fair value measurement, Assets, Other income, net	28	16
Fair value measurement, Assets, Other comprehensive loss	22	10
Fair value measurement, Assets, Purchases, sales, issuances, and settlements		596
Fair value measurement, Assets, Transfers into and (or) out of Level 3
Fair value measurement, Assets, Foreign currency translation	(41)	30
Balance at end of year	349	547
Fair value measurement, Assets, Sales
Fair value measurement, Assets, Cost of goods sold
Fair value measurement, Assets, Other income, net	28	16
Fair value measurement, Liabilities, Beginning balance	608	602
Fair value measurement, Liabilities, Sales	(24)	(33)
Fair value measurement, Liabilities, Other comprehensive loss	(174)	39
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	410	608
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	30	28
Fair value measurement, Liabilities, Cost of goods sold	(1)	(1)
Fair value measurement, Liabilities, Other income, net	(8)	3
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	21	30
Fair value measurement, Liabilities, Sales
Fair value measurement, Liabilities, Cost of goods sold
Fair value measurement, Liabilities, Other income, net	(8)	3
Energy Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of year	3	2
Fair value measurement, Assets, Other comprehensive loss	3	1
Fair value measurement, Assets, Purchases, sales, issuances, and settlements
Fair value measurement, Assets, Transfers into and (or) out of Level 3
Balance at end of year	6	3
Fair value measurement, Assets, Sales
Fair value measurement, Assets, Cost of goods sold