Restructuring and Other Charges - 2016 Actions - Additional Information (Detail) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) Employees Positions	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 685	$ 155	$ 214	$ 314
Restructuring and other charges after tax		114	192	249
Layoff costs		$ 70	97	105
United Kingdom [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees		60
Other exit costs		$ 4
Layoff costs		2
Alcoa Corporation [Member] | Tennessee [Member] | Toll Processing and Services Agreement [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 21
Number of employees associated with layoff costs | Positions		145
Other exit costs		$ 9
Layoff costs		7
RTI [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		3
Restructuring and other charges after tax		2
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		23	39	24
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		57
Restructuring and other charges after tax		46
Shutdown and Curtailment Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		37
Restructuring and other charges after tax		24
Restructuring Programs Layoffs 2015 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		53
Restructuring and other charges after tax		$ 33
Number of employees associated with layoff costs | Positions		1,315
Restructuring charges for layoffs		$ 55	18
Restructuring Programs Layoffs 2015 [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Positions		210
Restructuring Programs Layoffs 2015 [Member] | Transportation and Construction Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Positions		30
Restructuring Programs Layoffs 2015 [Member] | Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Positions		1,045
Restructuring Programs Layoffs 2015 [Member] | Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Positions		30
Other Adjustments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 25	8	10
Restructuring and other charges after tax		12	3	5
Other Miscellaneous Items [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		11	7	10
Restructuring and other charges after tax		8	$ 4	7
Pension Settlement Cost [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		2
Restructuring and other charges after tax		1
Closure Of Five Facility [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		20
Restructuring and other charges after tax		$ 14
Number of employees associated with layoff costs | Positions		280
Asset Impairment and Accelerated Depreciation [Member] | United Kingdom [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 51
Asset Retirement Obligations [Member] | Alcoa Corporation [Member] | Tennessee [Member] | Toll Processing and Services Agreement [Member]
Restructuring Cost and Reserve [Line Items]
Other exit costs		4
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		2		$ 18
Environmental Remediation [Member] | Alcoa Corporation [Member] | Tennessee [Member] | Toll Processing and Services Agreement [Member]
Restructuring Cost and Reserve [Line Items]
Other exit costs		3
Other Restructuring [Member] | Alcoa Corporation [Member] | Tennessee [Member] | Toll Processing and Services Agreement [Member]
Restructuring Cost and Reserve [Line Items]
Other exit costs		$ 2
Restructuring Programs Layoffs 2016 [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees		1,800
Approximate number of employees already laid off | Employees		880
Restructuring charges for layoffs		$ 16