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Derivatives and Other Financial Instruments - Schedule of Gain or Loss on Hedged Items and Derivative Contracts (Parenthetical) (Detail) (Sales [Member], Aluminum Contracts [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Sales [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in earnings related to the ineffective portion of hedging relationships	$ 20

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- Definition

Derivative instruments gain loss recognized in income related to ineffective portion.

+ References

No definition available.

+ Details

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Namespace Prefix:	aa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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- Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration