Restructuring and Other Charges - 2015 Actions - Additional Information (Detail) € in Millions, $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Jun. 30, 2014 t	May. 31, 2014 t	May. 31, 2013 t	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€) Employees t Divestiture	Dec. 31, 2015 USD ($) Employees t Divestiture	Dec. 31, 2014 USD ($) Employees	Dec. 31, 2013 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges				$ 735	€ 150	$ 1,195	$ 1,168	$ 782
Restructuring and other charges after tax and noncontrolling interest				$ 507		836	703	585
Amount related to legal matters						$ 201
Number of plant divestitures | Divestiture					3	3
Asset impairment charges						$ 335	406	116
Capacity of lines under review period			15 months		12 months	12 months
Capacity of lines under review | t			460,000		2,800,000	2,800,000
Capacity of smelting lines under review | t					500,000	500,000
Inventory write down						$ 90
Inventory write down after tax and noncontrolling interests						43
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 83	39	433
Sao Luis Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Curtailment capacity | t					74,000	74,000
Capacity of lines under review | t		85,000
Suriname [Member]
Restructuring Cost and Reserve [Line Items]
Curtailment capacity | t					1,330,000	1,330,000
Point Comfort, TX Refinery [Member]
Restructuring Cost and Reserve [Line Items]
Curtailment capacity | t					2,010,000	2,010,000
Remaining curtailment capacity | t					1,635,000	1,635,000
Wenatchee, WA Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Curtailment capacity | t					143,000	143,000
Warrick, IN Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Capacity closure | t					269,000	269,000
Pocos de Caldas Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Capacity closure | t					96,000	96,000
Capacity of lines under review | t	200,000	62,000
Point Henry Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Percentage of power supply					40.00%	40.00%
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 438	693	245
Restructuring and other charges after tax and noncontrolling interest						281	443	183
Shutdown and Curtailment Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						246	208
Restructuring and other charges after tax and noncontrolling interest						118
Asset impairment charges						$ 217	$ 166
Number of employees associated with layoff costs | Employees					3,100	3,100	1,790
Inventory write down							$ 67
Inventory write down after tax and noncontrolling interests							$ 47
Shutdown and Curtailment Actions [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees							30
Shutdown and Curtailment Actions [Member] | Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees							470
Shutdown and Curtailment Actions [Member] | Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees					1,800	1,800	1,210
Shutdown and Curtailment Actions [Member] | Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees					1,300	1,300	80
Shutdown and Curtailment Actions [Member] | Australia [Member]
Restructuring Cost and Reserve [Line Items]
Asset impairment charges						$ 34
Asset impairment charges after taxes and noncontrolling interests						14
Gain on sale of land						18
Gain on sale of land after tax						13
Divested Businesses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges							$ 332
Restructuring and other charges after tax and noncontrolling interest							163
Divested Businesses [Member] | Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						161
Restructuring and other charges after tax and noncontrolling interest						151
Other Miscellaneous Items [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						4	18	17
Restructuring and other charges after tax and noncontrolling interest						7	11	12
Other Adjustments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						14
Restructuring and other charges after tax and noncontrolling interest						11
Restructuring Programs Layoffs 2014 [Member]
Restructuring Cost and Reserve [Line Items]
Adjustments associated with divestitures						143
Adjustment associated with divestitures after tax and noncontrolling interest						$ 102
Number of positions | Employees					2,100	2,100
Restructuring charges for layoffs						$ 62	141
Restructuring Programs Layoffs 2014 [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions | Employees					475	475
Restructuring Programs Layoffs 2014 [Member] | Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions | Employees					90	90
Restructuring Programs Layoffs 2014 [Member] | Transportation and Construction Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions | Employees					425	425
Restructuring Programs Layoffs 2014 [Member] | Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions | Employees					645	645
Restructuring Programs Layoffs 2014 [Member] | Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions | Employees					380	380
Restructuring Programs Layoffs 2014 [Member] | Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions | Employees					85	85
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 156	51	87
Restructuring and other charges after tax and noncontrolling interest							36	61
Pension Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						30	26
Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						84	2
Restructuring and other charges after tax and noncontrolling interest							2
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						76	95	58
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						86	$ 47	$ 12
Supplier and Customer Contract [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 65
Restructuring Programs Layoffs 2015 [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions | Employees					1,500	1,500
Restructuring charges for layoffs						$ 42
Number of employees | Employees					5,200	5,200