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Note 3. Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Tables)
12 Months Ended
Dec. 31, 2011
Property, Plant and Equipment [Table Text Block]
   
December 31,
 
   
2011
   
2010
 
Mining properties, including asset retirement obligations
  $ 286,873     $ 276,869  
Development costs
    123,772       114,071  
Plants and equipment
    383,045       351,146  
Land
    11,188       10,301  
Mineral interests
    383,491       358,857  
Construction in progress
    125,045       65,346  
      1,313,414       1,176,590  
Less accumulated depreciation, depletion and amortization
    390,202       343,302  
Net carrying value
  $ 923,212     $ 833,288  
Operating Leases of Lessee Disclosure [Table Text Block]
Year ending December 31,
     
2012
  $ 2,691  
2013
    2,082  
2014
    2,076  
2015
    374  
2016
    347  
Thereafter
    1,010  
Total
  $ 8,580