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Major Lessee (Tables)
 12 Months Ended
Dec. 31, 2011
Major Lessees [Abstract]  
Revenues from lessees that exceeded ten percent of total revenues
                                                 
    For the Years Ended
December 31,		  
    2011     2010     2009  
    Revenues     Percent     Revenues     Percent     Revenues     Percent  
    (Dollars in thousands)  

Alpha Natural Resources

   $ 107,267       28.4 %    $ 79,084       26.2 %    $ 64,626       25.2 % 

The Cline Group

   $ 64,829       17.2 %    $ 62,372       20.7 %    $ 37,369       14.6 %