Restructuring and Other Charges - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	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		12 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		3 Months Ended		9 Months Ended		12 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		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	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Mar. 31, 2014 t	Sep. 30, 2013 t Location	Sep. 30, 2014 Employees t	Sep. 30, 2013 Employees Location	Dec. 31, 2013	Sep. 30, 2014 Engineered Products and Solutions [Member] Employees	Sep. 30, 2013 Engineered Products and Solutions [Member] Employees	Sep. 30, 2014 Global Rolled Products Segment [Member] Employees	Sep. 30, 2014 Alumina and Primary Metals Segments [Member] Employees	Sep. 30, 2014 Primary Metals [Member] Employees	Sep. 30, 2013 Primary Metals [Member] Employees	Sep. 30, 2014 Global Rolled Products [Member] Employees	Sep. 30, 2013 Global Rolled Products [Member] Employees	Sep. 30, 2014 Alumina [Member] Employees	Mar. 31, 2014 Fusina and Massena East [Member] t	Sep. 30, 2013 Fusina and Massena East [Member]	Sep. 30, 2013 Fusina and Massena East [Member]	Mar. 31, 2014 Point Henry Smelter [Member] t	Sep. 30, 2014 Pocos De Caldas Refinery [Member] t	Sep. 30, 2014 Australia [Member] Facilities	Sep. 30, 2014 Baie Comeau [Member] Potline	Jun. 30, 2013 Baie Comeau [Member] Potline t	Sep. 30, 2014 Quebec Canada [Member] t	Jun. 30, 2013 Quebec Canada [Member] t	Sep. 30, 2014 Fusina Italy [Member] t	Jun. 30, 2013 Fusina Italy [Member] t	Sep. 30, 2014 Portovesme [Member] t	Sep. 30, 2014 Other Exit Costs [Member]	Sep. 30, 2013 Other Exit Costs [Member]	Sep. 30, 2014 Other Exit Costs [Member]	Sep. 30, 2013 Other Exit Costs [Member]	Dec. 31, 2013 Other Exit Costs [Member]	Sep. 30, 2013 Legal Matter [Member]	Sep. 30, 2014 Asset Impairment [Member]	Sep. 30, 2013 Asset Impairment [Member]	Sep. 30, 2014 Layoff Costs [Member]	Sep. 30, 2013 Layoff Costs [Member]	Dec. 31, 2013 Layoff Costs [Member]	Sep. 30, 2014 Layoff Costs [Member] Primary Metals [Member]	Sep. 30, 2014 Layoff Costs [Member] Primary Metals [Member]	Sep. 30, 2014 Other Miscellaneous Items [Member]	Sep. 30, 2013 Other Miscellaneous Items [Member]	Sep. 30, 2013 Other Miscellaneous Items [Member]	Sep. 30, 2014 Small Layoff Reserves Related to Prior Periods [Member]	Sep. 30, 2013 Small Layoff Reserves Related to Prior Periods [Member]	Sep. 30, 2014 Small Layoff Reserves Related to Prior Periods [Member]	Sep. 30, 2013 Small Layoff Reserves Related to Prior Periods [Member]	Sep. 30, 2014 Permanent Shutdown and Planned Demolition of Idled Structures [Member]	Sep. 30, 2013 Permanent Shutdown and Planned Demolition of Idled Structures [Member]	Sep. 30, 2014 Permanent Shutdown and Planned Demolition of Idled Structures [Member]	Sep. 30, 2013 Permanent Shutdown and Planned Demolition of Idled Structures [Member]	Sep. 30, 2014 Operating Supplies [Member]	Sep. 30, 2013 Operating Supplies [Member]	Sep. 30, 2014 Operating Supplies [Member]	Sep. 30, 2013 Operating Supplies [Member]	Sep. 30, 2014 Asset Retirement Obligations [Member]	Sep. 30, 2013 Asset Retirement Obligations [Member]	Sep. 30, 2014 Asset Retirement Obligations [Member]	Sep. 30, 2013 Asset Retirement Obligations [Member]	Dec. 31, 2013 Asset Retirement Obligations [Member]	Sep. 30, 2014 Environmental Remediation [Member]	Sep. 30, 2013 Environmental Remediation [Member]	Sep. 30, 2014 Environmental Remediation [Member]	Sep. 30, 2013 Environmental Remediation [Member]	Dec. 31, 2013 Environmental Remediation [Member]	Sep. 30, 2014 Smelter Curtailments [Member] Employees	Sep. 30, 2014 Supplier And Customer Contract [Member]	Sep. 30, 2013 Supplier And Customer Contract [Member]	Sep. 30, 2014 Supplier And Customer Contract [Member]	Sep. 30, 2013 Supplier And Customer Contract [Member]	Sep. 30, 2014 Restructuring Programs Layoffs 2014 [Member] Employees	Sep. 30, 2014 Restructuring Programs Layoffs 2014 [Member] Employees	Sep. 30, 2013 Pension Costs [Member]	Sep. 30, 2014 Pension Costs [Member]	Sep. 30, 2013 Pension Costs [Member]	Dec. 31, 2013 Pension Costs [Member]	Sep. 30, 2014 Restructuring Programs Layoffs 2013 [Member] Employees	Sep. 30, 2014 Restructuring Programs Layoffs 2013 [Member] Employees	Sep. 30, 2013 Exit Costs [Member]	Sep. 30, 2013 Exit Costs [Member]	Sep. 30, 2013 Exit Costs [Member] Primary Metals [Member] Employees	Sep. 30, 2013 Exit Costs [Member] Primary Metals [Member] Employees	Sep. 30, 2014 Corporate [Member]	Sep. 30, 2013 Corporate [Member]	Sep. 30, 2014 Corporate [Member] Employees	Sep. 30, 2013 Corporate [Member] Employees	Sep. 30, 2014 Corporate [Member] Other Miscellaneous Items [Member]	Sep. 30, 2014 Rolling Mill [Member] Plant	Mar. 31, 2014 Rolling Mill [Member] Plant	Sep. 30, 2014 Rolling Mill [Member] Plant	Sep. 30, 2014 Smelter [Member] Plant	Sep. 30, 2014 Smelter [Member] Plant	Sep. 30, 2014 Refinery [Member] Smelter Curtailments [Member] Plant
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 209		$ 151	$ 780	$ 402																								$ 220	$ 152	$ 663	$ 238		$ 103	$ 33	$ 29	$ 18	$ 27		$ 60	$ 197	$ 4	$ 1	$ 9	$ 10	$ 2	$ 17	$ 4											$ 95		$ 58			$ 47		$ 12	$ 67													$ 107	$ 107			$ 2	$ 1	$ 34	$ 126	$ 16
Restructuring and other charges, after-tax and noncontrolling interest	175		108	503	283																								186	109	426	179		62	26	19	11	20				2	1	6	9	2	13	3																			44																					9
Number of plants permanently shut down and demolished																																																																																									2	2	2	2	3
Restructuring and other charges, gain on sale of assets	5
Restructuring and other charges, gain on sale of assets after-tax	4
Number of plants temporarily curtailed																																																																																													2	1
Number of employees associated with layoff costs					510		115	170	30	10		120		190																																																					245															520	520			90	30
Reduction in production - result of market conditions, in metric tons per year			460,000	460,000												84,000			190,000	200,000						84,000		150,000
Remaining smelting capacity subject to review				62,000
Additional smelting capacity subject to review				85,000
Reduction in combined capacity		200,000
Number of employees associated with layoff costs				1,780							1,200		470		80																																																																							30
Other layoff cost including reclassification in pension cost				216		185																									176		84				40		101																																			78	18	78	92
Accelerated depreciation	40		35	190	58
Other asset impairment charges	74			165													4	18
Other exit costs																																																	45	6	178	55					40	48	95	48		4	5	42	5			1	2	41	2
Inventory write-down - permanent shutdown and planned demolition of idled structures																																																					33	2	67	9
Inventory write-down, after-tax and non-controlling interests																																																					27	1	47	6
Additional charges related to shutdown actions				25
Number of facilities accelerated depreciation write off																					3
Number of non-U.S. locations permanently shutdown and demolished			2		3
Number of potlines to be shutdown and demolished																						1	2
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		44,000
Capacity of lines under review period			15 months
Total number of employees already laid off																																																																								1,300	1,300					1,390	1,390
Number of positions separated																																																																									2,025						1,620
Cash payments made against the layoff reserves																																																																								66	89					4	36
Minimum amount of cash payments expected to be paid beyond the end of the current annual period				75
Maximum amount of cash payments expected to be paid beyond the end of the current annual period				$ 80