Restructuring and Other Charges - Additional Information (Detail) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended				3 Months Ended				6 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended			6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended			6 Months Ended	3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013 USD ($) t Person Location	Jun. 30, 2012 USD ($) Person	Jun. 30, 2013 USD ($) Person	Jun. 30, 2012 USD ($) Person	Mar. 31, 2013 USD ($)	Mar. 31, 2013 EUR (€)	Jun. 30, 2013 Baie Comeau [Member] USD ($) t Potline	Jun. 30, 2013 Quebec Canada [Member] t	Jun. 30, 2013 Fusina Italy [Member] t	Jun. 30, 2012 Alumina [Member] Person	Jun. 30, 2012 Alumina [Member] Person	Jun. 30, 2013 Primary Metals [Member] Person	Jun. 30, 2012 Primary Metals [Member] Person	Jun. 30, 2013 Primary Metals [Member] Person	Jun. 30, 2012 Primary Metals [Member] Person	Jun. 30, 2013 Corporate [Member] Person	Jun. 30, 2012 Corporate [Member] Person	Jun. 30, 2013 Corporate [Member] Person	Jun. 30, 2012 Corporate [Member] Person	Jun. 30, 2013 Other Miscellaneous Items [Member] USD ($)	Jun. 30, 2012 Other Miscellaneous Items [Member] USD ($)	Jun. 30, 2013 Other Miscellaneous Items [Member] USD ($)	Jun. 30, 2012 Other Miscellaneous Items [Member] USD ($)	Jun. 30, 2013 Global Rolled Products Segment Member [Member] Person	Jun. 30, 2013 Global Rolled Products Segment Member [Member] Person	Jun. 30, 2013 Engineered Products and Solutions [Member] Person	Jun. 30, 2013 Engineered Products and Solutions [Member] Person	Jun. 30, 2012 Engineered Products and Solutions [Member] Person	Jun. 30, 2012 Lease Termination Costs [Member] USD ($)	Jun. 30, 2012 Lease Termination Costs [Member] USD ($)	Jun. 30, 2013 Layoff Costs [Member] USD ($)	Jun. 30, 2012 Layoff Costs [Member] USD ($)	Jun. 30, 2013 Layoff Costs [Member] USD ($)	Jun. 30, 2012 Layoff Costs [Member] USD ($)	Jun. 30, 2013 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Jun. 30, 2012 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Jun. 30, 2013 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Jun. 30, 2012 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Jun. 30, 2013 Legal Matter [Member] USD ($)	Jun. 30, 2013 Legal Matter [Member] USD ($)	Jun. 30, 2013 Asset Impairments [Member] USD ($)	Jun. 30, 2013 Accelerated Depreciation [Member] USD ($)	Jun. 30, 2013 Other exit costs [Member] USD ($)	Jun. 30, 2013 Other exit costs [Member] USD ($) Location	Jun. 30, 2013 Asset Impairments and Retirements Costs [Member] USD ($)	Jun. 30, 2013 Asset Impairments and Retirements Costs [Member] USD ($)	Jun. 30, 2013 Operating Supplies [Member] USD ($)	Jun. 30, 2013 Permanent Shutdown and Planned Demolition of Idled Structures [Member] USD ($)	Jun. 30, 2013 Environmental Remediation [Member] USD ($)	Jun. 30, 2013 Environmental Remediation [Member] USD ($)	Jun. 30, 2013 Asset Retirement Obligations [Member] USD ($)	Jun. 30, 2013 Asset Retirement Obligations [Member] USD ($)	Jun. 30, 2012 Smelter Curtailments [Member] USD ($) Person	Jun. 30, 2013 Restructuring Programs Layoffs 2013 [Member] USD ($) Person	Jun. 30, 2013 Restructuring Programs Layoffs 2013 [Member] USD ($) Person	Jun. 30, 2013 Restructuring Programs Layoffs 2012 [Member] USD ($) Person	Jun. 30, 2013 Restructuring Programs Layoffs 2012 [Member] USD ($) Person	Jun. 30, 2013 Restructuring Programs Layoffs 2011 [Member] USD ($)	Jun. 30, 2013 Restructuring Programs Layoffs 2011 [Member] USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 244	$ 15	$ 251	$ 25																									$ 9		$ 24	$ 6	$ 27	$ 17					$ 103	$ 103	$ 14	$ 23	$ 49	$ 86	$ 29	$ 29				$ 12		$ 54	$ 6
Restructuring and other charges, after-tax and noncontrolling interests	170	10	175	17																									5		18	4	20	12					62		14	16	40	70	19	19							4
Number of U.S. locations permanently shutdown and planned demolition	2																																											2
Number of employees associated with layoff costs	470	110	530	330						25	25	55	10	115	160	45	75	45	75					190	190	180	180	70																									150
Restructuring reserve, other adjustment																				4	1	8	2							9					2	1	2	3
Restructuring reserve, other adjustment, after-tax																				2	1	5	2							5					1	1	1	2
Restructuring and other charges, after-tax and noncontrolling interests					110	85																																	62	62
Number of potlines to be shutdown and demolished							2
Reduction in production - result of market conditions, in mt per year							105,000
Reduction in production - result of market conditions, in mt per year								280,000	44,000
Reduction in production - result of market conditions, in mt per year	460,000
Other asset impairment charges	23
Other asset impairment charges	14
Inventory write-down - permanent shutdown and planned demolition of idled structures	7
Inventory write-down, after-tax and non-controlling interests																																															5
Other exit costs							140																																									49	44		5
Other exit costs, after-tax and noncontrolling interests							100																																										36		4
Total number of employees already laid off																																																						120	120	560	560
Number of positions separated																																																							530		800
Cash payments made against the layoff reserves																																																						1	2	4	11	2	6
Minimum amount of cash payments expected to be paid beyond the end of the current annual period			55
Maximum amount of cash payments expected to be paid beyond the end of the current annual period			$ 60