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Mine Closing, Reclamation, and Gas Well Closing (Tables)
 12 Months Ended
Dec. 31, 2016
MINE CLOSING, RECLAMATION & GAS WELL CLOSING [Abstract]  
Schedule of Change in Asset Retirement Obligation [Table Text Block]
 
 
As of December 31,
 
 
2016
 
2015
Balance at beginning of period
 
$
429,967

 
$
454,832

Accretion expense
 
23,924

 
32,438

Payments
 
(15,882
)
 
(18,033
)
Revisions in estimated cash flows
 
36,320

 
(33,984
)
Other
 
(785
)
 
(5,286
)
Balance at end of period
 
$
473,544

 
$
429,967