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, 2012	Dec. 31, 2011	Dec. 31, 2010
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 87	$ 281	$ 207
Alumina [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	3	39	12
Primary Metals [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	20	212	145
Global Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	43	19	(11)
Engineered Products and Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	13	(3)	18
Segment Total [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	79	267	164
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 8	$ 14	$ 43