Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Contingency [Line Items]
Effective tax rate	47.00%	28.10%
Income tax benefit recognized	35.00%	35.00%
Income tax benefit recognized	$ 226,000,000	$ (77,000,000)
Operational losses in certain foreign jurisdictions	35,000,000	56,000,000
Russia [Member]
Income Tax Contingency [Line Items]
Income tax benefit recognized	0
Alcoa World Alumina and Chemicals [Member]
Income Tax Contingency [Line Items]
Discrete income tax charge	83,000,000
Alcoa [Member] | Alcoa World Alumina and Chemicals [Member]
Income Tax Contingency [Line Items]
Percent of equity investment in other entity	60.00%
Deferred tax liability	50,000,000
Deferred tax asset written off as valuation allowance	60.00%
Alumina Limited [Member] | Alcoa World Alumina and Chemicals [Member]
Income Tax Contingency [Line Items]
Percent of equity investment in other entity	40.00%
Foreign Jurisdictions [Member]
Income Tax Contingency [Line Items]
Income tax benefit recognized	0	0
United States [Member]
Income Tax Contingency [Line Items]
Discrete income tax benefit	$ 33,000,000