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Inventories
12 Months Ended
Dec. 31, 2011
Inventories [Abstract]  
Inventories
Note 4. Inventories
Inventories are stated at the lower of cost or market. In the United States, we manufacture certain finished products and parts inventories for drill bits, completion products, bulk materials, and other tools that are recorded using the last-in, first-out method, which totaled $160 million at December 31, 2011 and $108 million at December 31, 2010. If the average cost method had been used, total inventories would have been $36 million higher than reported at December 31, 2011 and $34 million higher than reported at December 31, 2010. The cost of the remaining inventory was recorded on the average cost method. Inventories consisted of the following:

   
December 31
 
Millions of dollars
 
2011
  
2010
 
Finished products and parts
 $1,801  $1,369 
Raw materials and supplies
  673   496 
Work in process
  96   75 
Total
 $2,570  $1,940 

Finished products and parts are reported net of obsolescence reserves of $108 million at December 31, 2011 and $88 million at December 31, 2010.