Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

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		31		26
Bauxite mining		32		15
Primary Metals:
Aluminum smelting		35		22
Power generation		31		22
Global Rolled Products		28		22
Engineered Products and Solutions		27		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		4		35
Primary Metals		7		36
Global Rolled Products		9		12
Engineered Products and Solutions		11		24