Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2012

Weighted-Average Useful Lives of Structures and Machinery and Equipment

The following table details the weighted-average useful lives of structures and machinery and equipment by reporting segment (numbers in years):

Segment	Structures		Machinery and equipment
Alumina:
Alumina refining		30		25
Bauxite mining		33		19
Primary Metals:
Aluminum smelting		35		21
Power generation		34		24
Global Rolled Products		32		21
Engineered Products and Solutions		29		18

Weighted-Average Useful Lives of Software and Other Intangible Assets

The following table details the weighted-average useful lives of software and other intangible assets by reporting segment (numbers in years):

Segment	Software		Other intangible assets
Alumina		10		-
Primary Metals		9		36
Global Rolled Products		10		13
Engineered Products and Solutions		9		19