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Commitments and Contingencies - Additional Information (Detail)
3 Months Ended 6 Months Ended 12 Months Ended
Aug. 10, 2010
$ / a
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2017
USD ($)
$ / t
Jun. 30, 2016
USD ($)
Jul. 31, 2016
USD ($)
Dec. 31, 2016
USD ($)
Loss Contingencies [Line Items]              
Expenses related to operating leases and rental agreements   $ 2,092,000 $ 1,632,000 $ 4,068,000 $ 3,437,000    
Restricted cash   485,000   485,000     $ 971,000
Permit bond              
Loss Contingencies [Line Items]              
Bond, carrying value   1,350,000   1,350,000      
Jackson County, Wisconsin | Performance Bond              
Loss Contingencies [Line Items]              
Bond, carrying value   4,400,000   4,400,000      
Monroe County, Wisconsin | Performance Bond              
Loss Contingencies [Line Items]              
Bond, carrying value   900,000   900,000      
Pipeline Common Carrier | Performance Bond              
Loss Contingencies [Line Items]              
Bond, carrying value   1,943,000   1,943,000      
Restricted cash   485,000   485,000     $ 971,000
Consulting Agreement              
Loss Contingencies [Line Items]              
Closing fee per acre | $ / a 1            
Reimbursed expenses   10,000 3,000 $ 16,000 0    
Tonnage fees per ton | $ / t       0.50      
Tonnage fees incurred   $ 113,000 $ 53,000 $ 229,000 $ 98,000    
Consulting Agreement | Minimum              
Loss Contingencies [Line Items]              
Tonnage fees           $ 200,000