Restructuring and Other Charges - Schedule of Restructuring and Other Charges by Reportable Segments, Pretax (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 1,168	$ 782	$ 172
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	1,125	348	79
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	43	434	93
Alumina [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	287	11	3
Primary Metals [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	553	295	20
Global Rolled Products [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	266	15	43
Engineered Products and Solutions [Member] | Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 19	$ 27	$ 13