Restructuring and Other Charges - Additional Information (Detail) $ in Millions		1 Months Ended				3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2015 Employees	Aug. 31, 2014	Jun. 30, 2014 t	May. 31, 2014 t	May. 31, 2013 t	Jun. 30, 2015 USD ($) Employees t	Jun. 30, 2014 USD ($) Employees Plant Facilities	Mar. 31, 2014 t	Jun. 30, 2015 USD ($) Employees t	Jun. 30, 2014 USD ($) Employees Plant Facilities	Dec. 31, 2014 Employees
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 217	$ 110		$ 394	$ 571
Restructuring and other charges, after-tax and noncontrolling interest						$ 141	$ 54		$ 299	$ 328
Number of employees associated with layoff costs | Employees						390	75		600
Capacity of lines under review | t					460,000
Number of employees associated with layoff costs | Employees										245
Capacity of lines under review period					15 months
Minimum amount of cash payments expected to be paid beyond the end of the current annual period									$ 20
Maximum amount of cash payments expected to be paid beyond the end of the current annual period									25
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 24	$ 3		$ 29	$ 32
Number of employees associated with layoff costs | Employees							30		50
Number of employees associated with layoff costs | Employees										90
Firth Rixson [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						10
Restructuring and other charges, after-tax and noncontrolling interest						$ 7
Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Number of plants permanently shut down and demolished | Plant							2			2
Number of plants temporarily curtailed | Plant										2
Rolling Mill [Member]
Restructuring Cost and Reserve [Line Items]
Number of plants permanently shut down and demolished | Plant							2			2
Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees						30	30		60
Number of employees associated with layoff costs | Employees										30
Other Segments [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees							15
Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees						150			150
Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees										10
Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees						210			340
Number of employees associated with layoff costs | Employees										115
Massena East Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Reduction in production - result of market conditions, in mt per year | t								84,000
Point Henry Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Power supplied as percentage of plant total power requirement		40.00%
Reduction in production - result of market conditions, in mt per year | t								190,000
Pocos De Caldas Refinery [Member]
Restructuring Cost and Reserve [Line Items]
Capacity of lines under review | t			200,000	62,000
Reduction in production - result of market conditions, in mt per year | t									96,000
Sao Luis Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges									$ 16
Restructuring and other charges, after-tax and noncontrolling interest									$ 13
Capacity of lines under review | t				85,000					74,000
Sao Luis Smelter [Member] | Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees									680
Massena East, Ny and Point Henry and Yennora, Australia and Portovesme [Member]
Restructuring Cost and Reserve [Line Items]
Reduction in production - result of market conditions, in mt per year | t								200,000
Suriname [Member]
Restructuring Cost and Reserve [Line Items]
Capacity of lines under review | t						443,000
Suriname [Member] | Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees						120			120
Sao Luis Smelter and Suriname [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees									800
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 179	$ 107		$ 179	$ 443
Restructuring and other charges, after-tax and noncontrolling interest						115	51		115	240
Other Miscellaneous Items [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						5	3		3	17
Restructuring and other charges, after-tax and noncontrolling interest						3	3		2	11
Shutdown And Curtailment Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges							$ 4			$ 137
Number of employees associated with layoff costs | Employees							1,830			1,830
Other asset impairment charges										$ 91
Other exit costs							$ 10			133
Inventory write-down - permanent shutdown and planned demolition of idled structures										34
Inventory write-down, after-tax and non-controlling interests										20
Accelerated depreciation							$ 91			$ 150
Shutdown And Curtailment Actions [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees							40			40
Shutdown And Curtailment Actions [Member] | Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees							470			470
Shutdown And Curtailment Actions [Member] | Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees							1,230			1,230
Shutdown And Curtailment Actions [Member] | Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | Employees							90			90
Shutdown And Curtailment Actions [Member] | Australia [Member]
Restructuring Cost and Reserve [Line Items]
Number of facilities accelerated depreciation write off | Facilities							3			3
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges									45	$ 95
Other exit costs						45			45	55
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges									29	47
Other exit costs						29			29	38
Supplier And Customer Contract [Member]
Restructuring Cost and Reserve [Line Items]
Other exit costs						11			8	40
Shutdown Costs [Member]
Restructuring Cost and Reserve [Line Items]
Other asset impairment charges						86			86
Other exit costs						82			82
Inventory write-down - permanent shutdown and planned demolition of idled structures						4			4
Inventory write-down, after-tax and non-controlling interests						2			2
Shutdown Costs [Member] | Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 11			$ 11
Number of employees associated with layoff costs | Employees						100			100
Smelter Curtailments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges										68
Restructuring and other charges, after-tax and noncontrolling interest										$ 44
Smelter Curtailments [Member] | Refinery [Member]
Restructuring Cost and Reserve [Line Items]
Number of plants temporarily curtailed | Plant										1
Asset Impairment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges										$ 33
Restructuring and other charges, after-tax and noncontrolling interest										26
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges									$ 38	17
Restructuring and other charges, after-tax and noncontrolling interest									23	11
Layoff Costs [Member] | Suriname [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						$ 18
Restructuring and other charges, after-tax and noncontrolling interest						10
Small Layoff Reserves Related to Prior Periods [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges						1			8	7
Restructuring and other charges, after-tax and noncontrolling interest						$ 1			$ 7	$ 4
Restructuring Programs Layoffs 2015 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off | Employees	730					730			730
Number of positions separated | Employees	1,500
Cash payments made against the layoff reserves						$ 14			$ 15
Restructuring Programs Layoffs 2014 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off | Employees	2,460					2,460			2,460
Number of positions separated | Employees	2,870										2,910
Cash payments made against the layoff reserves						$ 6			$ 56
Restructuring Programs Layoffs 2013 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off | Employees	1,460					1,460			1,460
Number of positions separated | Employees	1,530
Cash payments made against the layoff reserves						$ 2			$ 5
Divested Businesses [Member] | Russia [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges									159
Restructuring and other charges, after-tax and noncontrolling interest									$ 149