Investments - Additional Information (Detail) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended						12 Months Ended			1 Months Ended	12 Months Ended						1 Months Ended					12 Months Ended								12 Months Ended					12 Months Ended
	Jun. 30, 2013	Dec. 31, 2013 USD ($) Agency Subsidiary	Dec. 31, 2012 USD ($) Kmt	Dec. 31, 2011 USD ($)	Dec. 31, 2013 Becancour Smelter [Member]	Dec. 31, 2013 Boke Investment Company [Member]	Dec. 31, 2013 Compagnie Des Bauxites De Guinee [Member]	Dec. 31, 2013 Alcoa Joint Venture [Member] USD ($)	Dec. 31, 2013 Alcoa Joint Venture [Member] SAR	Dec. 31, 2012 Alcoa Joint Venture [Member] USD ($)	Oct. 31, 2011 Ma'aden Joint Venture [Member]	Dec. 31, 2013 Ma'aden Joint Venture [Member] USD ($)	Dec. 31, 2010 Ma'aden Joint Venture [Member]	Dec. 31, 2012 Smelting and Rolling Mill Companies [Member] USD ($)	Dec. 31, 2010 Smelting and Rolling Mill Companies [Member] USD ($)	Dec. 31, 2013 Other Noncurrent Liabilities and Deferred Credits [Member] USD ($)	Dec. 31, 2012 Other Noncurrent Liabilities and Deferred Credits [Member] USD ($)	Oct. 31, 2011 Refining and Mining Company [Member] USD ($)	Dec. 31, 2013 Refining and Mining Company [Member] USD ($)	Dec. 31, 2012 Refining and Mining Company [Member] USD ($)	Dec. 31, 2013 Fixed Income Securities [Member] USD ($)	Dec. 31, 2012 Equity Securities [Member] USD ($)	Dec. 31, 2011 Scenario One [Member] Saudi Arabia Joint Venture [Member] USD ($)	Dec. 31, 2011 Scenario Two [Member] Saudi Arabia Joint Venture [Member] USD ($)	Dec. 31, 2013 Alcoa World Alumina and Chemicals [Member] Alcoa Joint Venture [Member]	Dec. 31, 2013 Alcoa World Alumina and Chemicals [Member] Alumina Limited [Member]	Dec. 31, 2013 Smelter Sites [Member] Pechiney Reynolds Quebec, Inc. [Member]	Dec. 31, 2012 Smelter Sites [Member] Pechiney Reynolds Quebec, Inc. [Member]	Dec. 31, 2013 Smelter Sites [Member] Becancour Smelter in Quebec, Canada [Member]	Dec. 31, 2013 Smelter Sites [Member] Alcoa [Member]	Dec. 31, 2013 Bauxite Mining [Member] Kmt	Dec. 31, 2013 Bauxite Mining [Member] Halco Mining, Inc. [Member]	Dec. 31, 2012 Bauxite Mining [Member] Halco Mining, Inc. [Member]	Dec. 31, 2013 Bauxite Mining [Member] Minerao Rio Do Norte S.A. [Member]	Dec. 31, 2012 Bauxite Mining [Member] Minerao Rio Do Norte S.A. [Member]	Dec. 31, 2013 Alumina Refinery [Member] Kmt	Dec. 31, 2013 Primary Aluminum Smelter [Member] Kmt	Dec. 31, 2013 Rolling Mill [Member] Kmt
Schedule of Equity Method Investments [Line Items]
Percent of equity investments in other entity					49.90%	100.00%	51.00%																		60.00%	40.00%	50.00%	50.00%	50.10%	25.05%		45.00%	45.00%	18.20%	18.20%
Number of wholly-owned subsidiaries		2
Dividends from equity investments		$ 89	$ 101	$ 100
Joint venture shareholders agreement period, years												30 years
Joint venture shareholders agreement, automatic extension additional period, years												20 years
Projected capacity amount of processed bauxite, in kmt																															4,000					1,800	740	380
Expanded capacity amount of processed bauxite, in Kmt			100
Ownership interest in joint venture								25.10%	25.10%		74.90%	74.90%	74.90%		25.10%			25.10%
Initial investment								80
Payment for pro rata share of pre-incorporation costs												56
Ownership interest in joint venture at fair market value												14.90%
Period Bracket To Exercise Option												6 months
Period To Open Option Exercise Bracket From Commercial Production Date												5 years
Outstanding receivable for labor and other employee-related expenses		31	28
Capital investment		1,907	1,860					10,800	40,500
Amount invested by Alcoa and Aluminum Financing Limited								1,100
Capital investment commitment paid-to-date		171	253					832
Equity investments		1,777	1,782					951		816
Project financing														480	4,035			1,992
Portion of project financing representing Alcoa interest in venture														120	1,013			500
Debt service requirements, principal														121				60
Debt service requirements, interest maximum														60				25
Fair value of guarantee included in other noncurrent liabilities and deferred credits		370														10	10
Minimum number of rating agencies to meet commitment on downgrade rating		2
Combined fair value of guarantees																			4	4
Potential forfeiture of letter of credit																							350	60
Joint venture agreement period	20 years
Other investments		$ 130	$ 78																		$ 119	$ 67