Restructuring and Other Charges - Additional Information (Detail) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended	3 Months Ended				9 Months Ended	3 Months Ended	9 Months Ended					3 Months Ended	9 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended				3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2013 USD ($) Location	Jun. 30, 2013 t	Sep. 30, 2012 USD ($) Employees	Sep. 30, 2013 USD ($) Location Employees	Sep. 30, 2012 USD ($) Employees	Dec. 31, 2012 USD ($)	Sep. 30, 2013 EUR (€)	Sep. 30, 2013 Baie Comeau [Member] USD ($)	Jun. 30, 2013 Baie Comeau [Member] Potline t	Sep. 30, 2013 Baie Comeau [Member] USD ($)	Jun. 30, 2013 Quebec Canada [Member] t	Sep. 30, 2013 Fusina Italy [Member] Facility Potline t	Jun. 30, 2013 Fusina Italy [Member] t	Sep. 30, 2013 Fusina and Massena East [Member] USD ($)	Sep. 30, 2013 Fusina and Massena East [Member] USD ($)	Sep. 30, 2013 Other Miscellaneous Items [Member] USD ($)	Sep. 30, 2013 Other Miscellaneous Items [Member] USD ($)	Sep. 30, 2012 Other Miscellaneous Items [Member] USD ($)	Sep. 30, 2013 Engineered Products and Solutions [Member] Employees	Sep. 30, 2012 Engineered Products and Solutions [Member] Employees	Sep. 30, 2013 Global Rolled Products Segment [Member] Employees	Sep. 30, 2013 Primary Metals [Member] USD ($) Employee	Sep. 30, 2013 Primary Metals [Member] USD ($) Employees	Sep. 30, 2012 Primary Metals [Member] Employees	Sep. 30, 2013 Corporate [Member] Employees	Sep. 30, 2012 Corporate [Member] Employees	Sep. 30, 2012 Alumina [Member] Employees	Sep. 30, 2013 Layoff Costs [Member] USD ($)	Sep. 30, 2012 Layoff Costs [Member] USD ($)	Sep. 30, 2013 Layoff Costs [Member] USD ($)	Sep. 30, 2012 Layoff Costs [Member] USD ($)	Dec. 31, 2012 Layoff Costs [Member] USD ($)	Sep. 30, 2013 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Sep. 30, 2012 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Sep. 30, 2013 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Sep. 30, 2012 Small Layoff Reserves Related to Prior Periods [Member] USD ($)	Sep. 30, 2013 Small Layoff Reserves Related to Prior Periods [Member] Other Miscellaneous Items [Member] USD ($)	Sep. 30, 2013 Other Exit Costs [Member] USD ($)	Sep. 30, 2013 Other Exit Costs [Member] USD ($)	Dec. 31, 2012 Other Exit Costs [Member] USD ($)	Sep. 30, 2013 Legal Matter [Member] USD ($)	Sep. 30, 2013 Asset Impairments and Retirements Costs [Member] USD ($)	Sep. 30, 2013 Operating Supplies [Member] USD ($)	Sep. 30, 2013 Operating Supplies [Member] USD ($)	Sep. 30, 2013 Permanent Shutdown and Planned Demolition of Idled Structures [Member] USD ($)	Sep. 30, 2013 Asset Retirement Obligations [Member] USD ($)	Sep. 30, 2013 Environmental Remediation [Member] USD ($)	Sep. 30, 2013 Pension Costs [Member] USD ($)	Sep. 30, 2013 Pension Costs [Member] USD ($)	Sep. 30, 2012 Smelter Curtailments [Member] USD ($) Employees	Sep. 30, 2012 Lease Termination Costs [Member] USD ($)	Sep. 30, 2013 Restructuring Programs Layoffs 2013 [Member] USD ($) Employees	Sep. 30, 2013 Restructuring Programs Layoffs 2013 [Member] USD ($) Employees	Sep. 30, 2013 Restructuring Programs Layoffs 2012 [Member] USD ($) Employees	Sep. 30, 2013 Restructuring Programs Layoffs 2012 [Member] USD ($) Employees	Sep. 30, 2013 Restructuring Programs Layoffs 2011 [Member] USD ($)	Sep. 30, 2013 Restructuring Programs Layoffs 2011 [Member] USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 151		$ 2	$ 402	$ 27																							$ 107	$ 3	$ 27	$ 20							$ 152	$ 238		$ 103	$ 29				$ 58	$ 12			$ 9
Restructuring and other charges, after-tax and noncontrolling interests	108		2	283	19																								2	20	14							109	179			19								6
Number of U.S. locations permanently shutdown and planned demolition	2			3
Restructuring reserve, other adjustment																1	9	2															2	1	4	4															9
Restructuring reserve, other adjustment, after-tax																1		2															2	1	3	2	6														5
Restructuring and other charges, after-tax and noncontrolling interests	110			110			85																																		62
Number of employees associated with layoff costs			20	510	350														170	70	190	520	120	180	30	75	25																							160
Number of potlines to be shutdown and demolished									2			1
Reduction in production - result of market conditions, in mt per year									105,000			41,000
Reduction in production - result of market conditions, in mt per year											280,000	84,000	44,000
Number of facilities in which demolition and remediation activities will begin												3
Reduction in production - result of market conditions, in mt per year		460,000
Accelerated depreciation								35		58
Other asset impairment charges														4	18
Inventory write-down - permanent shutdown and planned demolition of idled structures																																											2	9
Inventory write-down, after-tax and non-controlling interests																																											1	6
Other exit costs																																													55	48	5
Pension cost																																																78	78
Write off of remaining book value of properties, plants & equipment				162		26																6	55							87		21							75	5									80
Other related costs				2
Total number of employees already laid off																																																				780	780	640	640
Number of positions separated																																																					1,030		800
Cash payments made against the layoff reserves																																																				10	12	2	13	2	8
Minimum amount of cash payments expected to be paid beyond the end of the current annual period				65
Maximum amount of cash payments expected to be paid beyond the end of the current annual period				$ 70