XML 1146 R154.htm IDEA: XBRL DOCUMENT v2.4.0.6

Derivatives and Other Financial Instruments - Schedule of Gain or Loss on Hedged Items and Derivative Contracts (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in earnings related to ineffective portion of hedging relationships		$ (1)	$ 1
Aluminum Contracts [Member] | Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in earnings related to ineffective portion of hedging relationships	$ (18)	$ 7	$ (3)

X

- Definition

Derivative Instruments Gain Loss Recognized In Income Related To Ineffective Portion

+ References

No definition available.

+ Details

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

X

- Details

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