Restructuring and Other Charges - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Person	Dec. 31, 2011 Person GeneratingPlant Location	Dec. 31, 2010 Location
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 87	$ 281	$ 207
Restructuring and other charges, after-tax and noncontrolling interests	73	181	130
Number of employees associated with layoff costs	800	1,600
Restructuring reserve, other adjustment		23	33
Restructuring reserve, other adjustment, after-tax		16	24
Number of U.S. locations permanently shutdown and planned demolition		2	5
Other exit costs		5	2
Other exit costs, after-tax and noncontrolling interests		4	2
Inventory write-down - permanent shutdown and planned demolition of idled structures			8
Inventory write-down, after-tax and non-controlling interests			5
Number of European smelters, management approved, partial or full curtailment		3
Number of smelters in Spain where curtailment is planned to be temporary		2
Layoff costs of positions eliminations		33
Layoff costs of positions eliminations, after-tax		31
Number of employees layoff		650
Asset impairments	40	150	139
Minimum amount of cash payments expected to be paid beyond the end of the current annual period	50
Maximum amount of cash payments expected to be paid beyond the end of the current annual period	55
Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	20	212	145
Number of employees associated with layoff costs	250	820	75
Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	43	19	(11)
Number of employees associated with layoff costs		470	25
Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3	39	12
Number of employees associated with layoff costs	85	160	60
Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	13	(3)	18
Number of employees associated with layoff costs	390	20	625
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	8	14	43
Number of employees associated with layoff costs	75	130	90
Divested Businesses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			22
Restructuring and other charges, after-tax and noncontrolling interests			14
Asset impairments			12
Asset impairments, after-tax			8
Other Miscellaneous Items [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	4
Restructuring reserve, other adjustment, after-tax	4
Rockdale, TX [Member]
Restructuring Cost and Reserve [Line Items]
Number of U.S. locations permanently shutdown and planned demolition		2
Number of potlines to be shutdown and demolished		2
Number of potlines at facility		4
Warrick, IN [Member]
Restructuring Cost and Reserve [Line Items]
Number of potlines to be shutdown and demolished			1
Asset Impairments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		127
Restructuring and other charges, after-tax and noncontrolling interests		82
Restructuring reserve, other adjustment	30
Restructuring reserve, other adjustment, after-tax	30
Asset impairments			127
Asset impairments, after-tax			80
Other Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		36	46
Restructuring and other charges, after-tax and noncontrolling interests		23	29
Other exit costs		1
Other exit costs, after-tax and noncontrolling interests		1
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	47	93
Restructuring and other charges, after-tax and noncontrolling interests	29	68
Other Asset Impairments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		23
Restructuring and other charges, after-tax and noncontrolling interests		12
Restructuring reserve, other adjustment	10
Restructuring reserve, other adjustment, after-tax	8
Litigation Matter [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		20
Restructuring and other charges, after-tax and noncontrolling interests		8
Permanent Shutdown and Planned Demolition of Idled Structures [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			2
Other exit costs		36	46
Other asset impairment charges		127	127
Other restructuring activities, after-tax and noncontrolling interests			1
Permanent Shutdown and Planned Demolition of Idled Structures [Member] | Alcoa, TN [Member]
Restructuring Cost and Reserve [Line Items]
Reduction in production - result of market conditions, in kmt per year		215
Permanent Shutdown and Planned Demolition of Idled Structures [Member] | Rockdale, TX [Member]
Restructuring Cost and Reserve [Line Items]
Reduction in production - result of market conditions, in kmt per year		76
Permanent Shutdown and Planned Demolition of Idled Structures [Member] | Remaining Capacity [Member]
Restructuring Cost and Reserve [Line Items]
Reduction in production - result of market conditions, in kmt per year		191
Permanent Shutdown and Planned Demolition of Idled Structures [Member] | Frederick, MD [Member]
Restructuring Cost and Reserve [Line Items]
Reduction in production - result of market conditions, in kmt per year			195
Permanent Shutdown and Planned Demolition of Idled Structures [Member] | Badin, NC [Member]
Restructuring Cost and Reserve [Line Items]
Reduction in production - result of market conditions, in kmt per year			60
Permanent Shutdown and Planned Demolition of Idled Structures [Member] | Warrick, IN [Member]
Restructuring Cost and Reserve [Line Items]
Reduction of production plan included in asset impairment, kmt			40
Operating Supplies [Member]
Restructuring Cost and Reserve [Line Items]
Inventory write-down - permanent shutdown and planned demolition of idled structures		6
Inventory write-down, after-tax and non-controlling interests		4
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		18
Restructuring and other charges, after-tax and noncontrolling interests			14
Other exit costs		18	14
Other exit costs, after-tax and noncontrolling interests		11	9
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		17
Restructuring and other charges, after-tax and noncontrolling interests			30
Other exit costs		17	30
Other exit costs, after-tax and noncontrolling interests		11	19
Restructuring Programs Layoffs 2010 [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs			875
Cash payments made against the layoff reserves	3	7
Restructuring Programs Layoffs 2010 [Member] | Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			43
Restructuring and other charges, after-tax and noncontrolling interests			29
Restructuring Programs Layoffs 2012 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off	270
Number of positions separated	800
Cash payments made against the layoff reserves	16
Smelter Curtailments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	10
Restructuring and other charges, after-tax and noncontrolling interests	7
Number of employees associated with layoff costs	170
Lease and Contract Termination Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	6
Restructuring reserve, other adjustment, after-tax	6
Small Layoff Reserves Related to Prior Periods [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	21
Restructuring reserve, other adjustment, after-tax	15
Portovesme Smelter [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	11
Restructuring reserve, other adjustment, after-tax	11
Portovesme, Italy [Member]
Restructuring Cost and Reserve [Line Items]
Capacity for which management approved partial or full curtailment, in kmt		150
Aviles, Spain [Member]
Restructuring Cost and Reserve [Line Items]
Capacity for which management approved partial or full curtailment, in kmt		46
Capacity of smelters for which management approved partial or full curtailment, in kmt		93
La Coruna, Spain [Member]
Restructuring Cost and Reserve [Line Items]
Capacity for which management approved partial or full curtailment, in kmt		44
Capacity of smelters for which management approved partial or full curtailment, in kmt		87
Restructuring Programs (Layoffs), 2011 [Member]
Restructuring Cost and Reserve [Line Items]
Total number of employees already laid off	895
Number of positions separated	1,475
Cash payments made against the layoff reserves	23	24
Spain [Member] | Smelter Operation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, other adjustment	10
Restructuring reserve, other adjustment, after-tax	$ 7
Total number of employees already laid off	55