Restructuring and Other Charges - Schedule of Restructuring and Other Charges by Reportable Segments, Pretax (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 217	$ 110	$ 394	$ 571
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	193	107	365	539
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	24	3	29	32
Alumina [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	10		17	7
Primary Metals [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	173	84	198	415
Global Rolled Products [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	1	$ 23	136	113
Engineered Products and Solutions [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 9		$ 14	$ 4