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Commitments and Contingencies - Additional Information (Detail)
3 Months Ended 6 Months Ended 12 Months Ended
Aug. 01, 2010
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2018
USD ($)
$ / Ton
Jun. 30, 2017
USD ($)
Jul. 31, 2016
USD ($)
Dec. 31, 2017
USD ($)
Loss Contingencies [Line Items]              
Expenses related to operating leases and rental agreements   $ 3,363,000 $ 2,092,000 $ 6,693,000 $ 4,068,000    
Capital required as well as future expansion projects   29,217,000   29,217,000      
Restricted cash   0   0     $ 487,000
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   0   0     $ 487,000
Consulting Agreement              
Loss Contingencies [Line Items]              
Closing fee per acre $ 1,000            
Consulting fees expenses reimbursements and closing cost   0 0 $ 60,000 16,000    
Tonnage fees per ton | $ / Ton       0.5      
Tonnage fees incurred   $ 204,000 $ 113,000 $ 368,000 $ 229,000    
Consulting Agreement | Minimum              
Loss Contingencies [Line Items]              
Tonnage fees           $ 200,000