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	Jun. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Fair value liability derivatives	$ 457	$ 479
Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	30	66
Level 3 [Member]
Derivative [Line Items]
Fair value liability derivatives	436	431
Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Fair value liability derivatives	448	469
Derivatives Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	16	45
Derivatives Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 3 [Member]
Derivative [Line Items]
Fair value liability derivatives	26	23
Derivatives Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Foreign Exchange Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	4
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	6	14
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	396	387
Derivatives Not Designated as Hedging Instruments [Member]
Derivative [Line Items]
Fair value liability derivatives	18	28
Derivatives Not Designated as Hedging Instruments [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	2	4
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	2	3
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	2
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	12	19
Margin Posted [Member] | Other Current Liabilities [Member] | Aluminum Contracts [Member] | Level 1 [Member]
Derivative [Line Items]
Fair value liability derivatives	$ 9	$ 18