XML 17 R55.htm IDEA: XBRL DOCUMENT v3.3.0.814

Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Settlements excluded from restructuring and other charges	$ 2	$ 2

X

- Definition

Defined benefit plan, recognized net gain (loss) due to settlements excluded from restructuring and other charges.

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

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