Investments - Additional Information (Detail) SAR in Millions, AUD in Millions, $ in Millions	1 Months Ended			3 Months Ended		12 Months Ended										93 Months Ended
	Apr. 30, 2016 USD ($) Refinery	Apr. 30, 2016 AUD Refinery	Jun. 30, 2013	Mar. 31, 2016 USD ($)	Mar. 31, 2016 AUD	Dec. 31, 2016 USD ($) kt	Dec. 31, 2016 AUD kt	Dec. 31, 2015 USD ($)	Dec. 31, 2015 AUD	Dec. 31, 2015 SAR	Dec. 31, 2014 USD ($)	Dec. 31, 2014 AUD	Dec. 31, 2012 kt	Dec. 31, 2004 USD ($)	Dec. 31, 2004 AUD	Sep. 30, 2011 USD ($)	Sep. 30, 2011 AUD	Dec. 31, 2016 AUD	Dec. 31, 2015 AUD	Dec. 31, 2015 SAR
Schedule of Equity Method Investments [Line Items]
Dividends from equity investments						$ 74		$ 152			$ 86
Expanded capacity amount of processed bauxite, in Kmt | kt													100
Outstanding receivable for labor and other employee-related expenses						$ 11		19
Number of alumina refineries to be powered under supplied agreement | Refinery	3	3
Ma'aden Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Joint venture shareholders agreement period, years						30 years	30 years
Joint venture shareholders agreement, automatic extension additional period, years						20 years	20 years
Ownership interest in joint venture						74.90%	74.90%
Alcoa Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture						25.10%	25.10%
Maaden Alcoa Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest in joint venture at fair market value						14.90%	14.90%
Period Bracket To Exercise Option						6 months	6 months
Period To Open Option Exercise Bracket From Commercial Production Date						5 years	5 years
Amount invested by Alcoa and Aluminum Financing Limited						$ 10,800				SAR 40,500
Capital investment						1				SAR 29
Equity investments						853														SAR 928
Ma'aden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member]
Schedule of Equity Method Investments [Line Items]
Project financing Investment						4,133
Ma'aden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member] | Other Noncurrent Liabilities and Deferred Credits [Member]
Schedule of Equity Method Investments [Line Items]
Guarantee issued on behalf of smelting and rolling mill companies						3		7
Maaden Alcoa Joint Venture Mine And Refinery Company [Member] | Other Noncurrent Liabilities and Deferred Credits [Member]
Schedule of Equity Method Investments [Line Items]
Guarantee issued on behalf of smelting and rolling mill companies						$ 3		3
Alumina Limited [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of amount required to be contributed in the event Alcoa would be required to make payments under the guarantees						40.00%	40.00%
Saudi Arabia Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Joint venture agreement period			20 years
Dampier to Bunbury Natural Gas Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Capital investment														$ 17	AUD 24
Dampier to Bunbury Natural Gas Pipeline [Member] | Three-Year Equity Call Plan [Member]
Schedule of Equity Method Investments [Line Items]
Amount invested by Alcoa and Aluminum Financing Limited											39	AUD 40
Dampier to Bunbury Natural Gas Pipeline [Member] | New Equity Call Plan [Member]
Schedule of Equity Method Investments [Line Items]
Amount invested by Alcoa and Aluminum Financing Limited						$ 3	AUD 5	16	AUD 21		$ 30	AUD 36
Capital investment				$ 20	AUD 27
Financial Guarantee [Member] | Ma'aden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member]
Schedule of Equity Method Investments [Line Items]
Debt service requirements, principal						100
Debt service requirements, interest maximum						35
Financial Guarantee [Member] | Maaden Alcoa Joint Venture Mine And Refinery Company [Member]
Schedule of Equity Method Investments [Line Items]
Debt service requirements, principal						120
Debt service requirements, interest maximum						30
Alcoa Corporation [Member] | Maaden Alcoa Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Amount invested by Alcoa and Aluminum Financing Limited						1,100
Capital investment						982
Alcoa Corporation [Member] | Ma'aden Alcoa Joint Venture Smelter And Rolling Mill Companies [Member]
Schedule of Equity Method Investments [Line Items]
Project financing Investment						1,037
Alcoa Corporation [Member] | Maaden Alcoa Joint Venture Mine And Refinery Company [Member]
Schedule of Equity Method Investments [Line Items]
Project financing Investment						2,232
Scenario Two [Member] | Saudi Arabia Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Potential forfeiture of letter of credit						$ 60
Bauxite Mining [Member]
Schedule of Equity Method Investments [Line Items]
Projected capacity amount of processed bauxite, in kmt | kt						4,000	4,000
Refining Facilities [Member]
Schedule of Equity Method Investments [Line Items]
Projected capacity amount of processed bauxite, in kmt | kt						1,800	1,800
Primary Aluminum Smelter [Member]
Schedule of Equity Method Investments [Line Items]
Projected capacity amount of processed bauxite, in kmt | kt						740	740
Rolling Mill [Member]
Schedule of Equity Method Investments [Line Items]
Projected capacity amount of processed bauxite, in kmt | kt						380	380
AWAC [Member] | Maaden Alcoa Joint Venture Mine And Refinery Company [Member]
Schedule of Equity Method Investments [Line Items]
Project financing Investment						$ 560
AofA [Member]
Schedule of Equity Method Investments [Line Items]
Investment percentage in DBP to be sold	20.00%	20.00%
Amount to be received by sale of investment percentage in DBP	$ 145	AUD 192
Gain after tax and noncontrolling interest						11	AUD 15
Pretax gain on sale of investments						27	AUD 35
AofA [Member] | Dampier to Bunbury Natural Gas Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Capital investment																$ 141	AUD 176
Investment percentage	30.00%	30.00%												20.00%	20.00%
Prepayments made under the agreement for future gas transmission services						$ 270		$ 268										AUD 375	AUD 368