Derivatives and Other Financial Instruments - Schedule of Fair Values and Corresponding Level of Fair Value Hierarchy of Outstanding Derivative Contracts Recorded as Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Fair value liability derivatives	$ 479	$ 679
Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	66	15
Level 3 [Member]
Derivative [Line Items]
Fair value liability derivatives	431	638
Level 2 [Member]
Derivative [Line Items]
Fair value liability derivatives		26
Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Fair value liability derivatives	469	622
Derivatives Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	45	13
Derivatives Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 3 [Member]
Derivative [Line Items]
Fair value liability derivatives	23	35
Derivatives Designated as Hedging Instruments [Member] | Other Noncurrent Liabilities and Deferred Credits [Member] | Aluminum Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	14	1
Derivatives Designated as Hedging Instruments [Member] | Other Noncurrent Liabilities and Deferred Credits [Member] | Aluminum Contracts [Member] | Level 3 [Member]
Derivative [Line Items]
Fair value liability derivatives	387	573
Derivatives Not Designated as Hedging Instruments [Member]
Derivative [Line Items]
Fair value liability derivatives	28	57
Derivatives Not Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	4	1
Derivatives Not Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 2 [Member]
Derivative [Line Items]
Fair value liability derivatives		21
Derivatives Not Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Embedded Credit Derivative [Member] | Level 3 [Member]
Derivative [Line Items]
Fair value liability derivatives	2	3
Derivatives Not Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Foreign Exchange Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	3
Derivatives Not Designated as Hedging Instruments [Member] | Other Noncurrent Liabilities and Deferred Credits [Member] | Aluminum Contracts [Member] | Level 2 [Member]
Derivative [Line Items]
Fair value liability derivatives		5
Derivatives Not Designated as Hedging Instruments [Member] | Other Noncurrent Liabilities and Deferred Credits [Member] | Embedded Credit Derivative [Member] | Level 3 [Member]
Derivative [Line Items]
Fair value liability derivatives	19	27
Margin Posted [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	$ 18