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Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2021
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 type of operation (numbers in years):

 

 

Structures

 

 

Machinery

and

equipment

 

Bauxite mining

 

 

33

 

 

 

17

 

Alumina refining

 

 

28

 

 

 

29

 

Aluminum smelting and casting

 

 

37

 

 

 

23

 

Energy generation

 

 

33

 

 

 

24

 

 
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 type of operation (numbers in years):

 

 

Software

 

 

Other intangible

assets

 

Bauxite mining

 

 

3

 

 

 

—

 

Alumina refining

 

 

6

 

 

 

3

 

Aluminum smelting and casting

 

 

3

 

 

 

40

 

Energy generation

 

 

3

 

 

 

29