Restructuring and Other Charges - Schedule of Restructuring and Other Charges by Reportable Segments, Pretax (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 7	$ 10
Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges
Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		5
Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3	1
Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3	3
Segment Total [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	6	9
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 1	$ 1