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Supplemental Schedule Of Cash Flow Information (Tables)
 3 Months Ended
Mar. 31, 2012
Supplemental Schedule Of Cash Flow Information [Abstract]  
Schedule Of Supplemental Cash Flow Information
     Three Months Ended March 31,  
     2012      2011  
     (In thousands)  

Capital leases issued for equipment

    $ 8,339       $ 12,230   

Asset retirement obligation additions

    $ 11       $ —