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Income Taxes - Reconciliation of Unrecognized Tax Benefits (Excluding Interest and Penalties) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 63us-gaap_UnrecognizedTaxBenefits	$ 66us-gaap_UnrecognizedTaxBenefits	$ 51us-gaap_UnrecognizedTaxBenefits
Additions for tax positions of the current year	2us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	2us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions
Additions for tax positions of prior years	5us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	11us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	39us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions
Reductions for tax positions of prior years	(4)us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	(2)us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	(7)us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions
Settlements with tax authorities	(29)us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities	(8)us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities	(18)us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities
Expiration of the statute of limitations		(2)us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations
Foreign currency translation	(2)aa_UnrecognizedTaxBenefitsForeignCurrencyTranslation	(4)aa_UnrecognizedTaxBenefitsForeignCurrencyTranslation	1aa_UnrecognizedTaxBenefitsForeignCurrencyTranslation
Balance at end of year	$ 35us-gaap_UnrecognizedTaxBenefits	$ 63us-gaap_UnrecognizedTaxBenefits	$ 66us-gaap_UnrecognizedTaxBenefits

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Unrecognized tax benefits foreign currency translation.

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854



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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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