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Inventories
 12 Months Ended
Dec. 31, 2017
Inventory Disclosure [Abstract]  
Inventories

I. Inventories

 

December 31,    2017     2016  

Finished goods

    $ 296     $ 226  

Work-in-process

      258       220  

Bauxite and alumina

      585       429  

Purchased raw materials

      473       363  

Operating supplies

      147       137  

LIFO reserve

      (306 )      (215 ) 
     $ 1,453     $ 1,160  

At December 31, 2017 and 2016, the total amount of inventories valued on a LIFO basis was $516, or 29%, and $393, or 29%, respectively, of total inventories before LIFO adjustments. The inventory values, prior to the application of LIFO, are generally determined under the average cost method, which approximates current cost.