Restructuring and Other Charges - Schedule of Restructuring and Other Charges by Reportable Segments, Pretax (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 18	$ 66	$ 134	$ 460
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	12	57	131	422
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	6	9	3	38
Alumina [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(1)	38	3	55
Primary Metals [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	17	11	105	209
Global Rolled Products [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(1)	(17)	1	119
Engineered Products and Solutions [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	(1)	22	16	33
Transportation and Construction Solutions [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ (2)	$ 3	$ 6	$ 6