Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Segment
Corporate [Member]
Goodwill [Line Items]
Segment reporting, goodwill	1,247
Alumina [Member]
Goodwill [Line Items]
Segment reporting, goodwill	161
Primary Metals [Member]
Goodwill [Line Items]
Segment reporting, goodwill	751
Global Rolled Products [Member]
Goodwill [Line Items]
Segment reporting, goodwill	62
Engineered Products and Solutions [Member]
Goodwill [Line Items]
Segment reporting, goodwill	273
Alcoa [Member]
Goodwill [Line Items]
Number of reportable segments	4