Contingencies and Commitments - Additional Information - 2 (Detail)	3 Months Ended									0 Months Ended	1 Months Ended				0 Months Ended					0 Months Ended		3 Months Ended	1 Months Ended		0 Months Ended		36 Months Ended		3 Months Ended		12 Months Ended		31 Months Ended	12 Months Ended			3 Months Ended				3 Months Ended			12 Months Ended	3 Months Ended		12 Months Ended		1 Months Ended		3 Months Ended
	Mar. 31, 2014 USD ($) Agency Entity	Mar. 31, 2014 EUR (€)	Dec. 31, 2013 USD ($)	Jun. 30, 2012 USD ($)	Jun. 30, 2012 EUR (€)	Mar. 31, 2014 Other Noncurrent Liabilities and Deferred Credits [Member] USD ($)	Dec. 31, 2013 Other Noncurrent Liabilities and Deferred Credits [Member] USD ($)	Mar. 31, 2014 State and Local Jurisdiction [Member] USD ($)	Mar. 31, 2014 State and Local Jurisdiction [Member] BRL	Apr. 08, 2013 Alcoa World Alumina Brasil [Member] BRL	Mar. 31, 2013 Alcoa World Alumina Brasil [Member] USD ($)	Mar. 31, 2013 Alcoa World Alumina Brasil [Member] BRL	May 31, 2012 Alcoa World Alumina Brasil [Member] USD ($)	May 31, 2012 Alcoa World Alumina Brasil [Member] BRL	Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Minimum [Member] USD ($)	Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Maximum [Member] USD ($)	Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] BRL	Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] Minimum [Member] USD ($)	Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] Maximum [Member] USD ($)	Feb. 27, 2014 Ligestra [Member] USD ($)	Feb. 27, 2014 Ligestra [Member] EUR (€)	Mar. 31, 2014 Ligestra [Member]	Jan. 31, 2014 Ligestra [Member] Minimum [Member]	Jan. 31, 2014 Ligestra [Member] Maximum [Member]	Feb. 27, 2014 Italian Ministry of Environment and Protection of Land and Sea[Member] USD ($)	Feb. 27, 2014 Italian Ministry of Environment and Protection of Land and Sea[Member] EUR (€)	Dec. 31, 2002 Alcoa Aluminio [Member] t	Mar. 31, 2014 Alcoa [Member] USD ($)	Mar. 31, 2014 Estreito Project [Member] USD ($) MWh	Mar. 31, 2014 Estreito Project [Member] BRL	Dec. 31, 2013 Estreito Project [Member] USD ($)	Dec. 31, 2013 Estreito Project [Member] BRL	Mar. 31, 2013 Estreito Project [Member] USD ($) MWh	Dec. 31, 2009 Fusina [Member] USD ($)	Dec. 31, 2012 Baie Comeau [Member] USD ($)	Dec. 31, 2012 Mosjoen [Member] USD ($)	Mar. 31, 2014 Ma'aden Joint Venture [Member] Entity	Mar. 31, 2014 Smelting and Rolling Mill Companies [Member] USD ($)	Mar. 31, 2014 Smelting and Rolling Mill Companies [Member] Other Noncurrent Liabilities and Deferred Credits [Member] USD ($)	Dec. 31, 2013 Smelting and Rolling Mill Companies [Member] Other Noncurrent Liabilities and Deferred Credits [Member] USD ($)	Mar. 31, 2014 Alcoa Joint Venture [Member] USD ($)	Mar. 31, 2014 Alcoa Joint Venture [Member] SAR	Dec. 31, 2013 Alcoa Joint Venture [Member] USD ($)	Dec. 31, 2009 Portovesme [Member] USD ($)	Mar. 31, 2014 Refining and Mining Company [Member] USD ($)	Mar. 31, 2014 Alumina Limited [Member]	Dec. 31, 2004 Dampier to Bunbury Natural Gas Pipeline [Member] USD ($)	Dec. 31, 2004 Dampier to Bunbury Natural Gas Pipeline [Member] AUD	Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] USD ($)	Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] AUD	Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] USD ($)	Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] AUD
Loss Contingencies [Line Items]
Remediation reserve increase (decrease)	$ 38,000,000																																	$ 12,000,000	$ 25,000,000	$ 20,000,000								$ 3,000,000
Percentage of payments and remediation costs																							50.00%	80.00%
Soil remediation project, estimated cost																									33,000,000	24,000,000
Payment for emergency action and natural resource damages																									25,000,000	18,000,000
Costs and payments																				17,000,000	12,000,000
Costs and payments related to damages																				9	6
Payment period																						10 years
Disallowed tax credits											110,000,000	220,000,000					175,000,000	0	80,000,000
Percentage of penalty of the gross disallowed amount											50.00%	50.00%
Value added tax receivable													41,000,000	82,000,000
Estimated range of reasonably possible loss, minimum										155,000,000					0	70,000,000
Administrative appeal, assessment period										2 years
Total combined assessments	333,000,000	242,000,000						55,000,000	125,000,000
Metal sold per month																											2,000
Investment percentage																													25.49%	25.49%			25.49%														20.00%	20.00%
Assured power from installed capacity																													150	150			150
Estimated project costs																													2,290,000,000	5,170,000,000		5,170,000,000	2,290,000,000
Aluminio's share of project																													580,000,000	1,320,000,000		1,320,000,000	580,000,000
Commitment expended on the project																													560,000,000	1,270,000,000	560,000,000	1,270,000,000
Ownership interest issued as guarantee for smelting and rolling mill companies																																					74.90%	25.10%			25.10%
Number of joint venture entities	3																																				3
Capital investment	1,949,000,000		1,907,000,000																																			4,515,000,000			10,800,000,000	40,500,000,000			1,992,000,000
Amount invested by Alcoa and Aluminum Financing Limited																																									1,100,000,000
Capital investment commitment paid-to-date																																									886,000,000
Capital investment commitment paid in period																																									54,000,000
Equity method investment, carrying value																																									967,000,000		951,000,000
Guarantee issued on behalf of smelting and rolling mill companies						3,000,000	4,000,000																					1,133,000,000											8,000,000	10,000,000					500,000,000
Debt service requirements, principal	60,000,000																																					121,000,000							67,000,000
Debt service requirements, interest maximum																																						60,000,000							30,000,000
Project financing	240,000,000
Ownership interest in joint venture at fair market value																																														40.00%
Number of agencies	2
Maximum percentage of equity investment	67.00%
Minimum percentage of equity Investment	67.00%
Initial cash investment																																															17,000,000	24,000,000
Additional contributions																																															141,000,000	176,000,000	31,000,000	31,000,000	2,000,000	2,000,000
Required plan contributions																																																			40,000,000	40,000,000
Prepayments made under the agreement for future gas transmission services																																																	327,000,000	355,000,000	327,000,000	355,000,000
Alcoa's maximum exposure to loss in projects				$ 417,000,000	€ 303,000,000																																												$ 460,000,000	500,000,000	$ 460,000,000	500,000,000