Quarterly report pursuant to Section 13 or 15(d)

Subsequent Events (Details)

v3.10.0.1
Subsequent Events (Details) - USD ($)
Jul. 16, 2018
Jul. 10, 2018
Jul. 09, 2018
Aug. 14, 2018
Aug. 07, 2018
Jun. 30, 2018
Subsequent Event [Line Items]            
Lease aggregate commitments           $ 72,942,000
Purchase obligation           $ 31,944,000
Subsequent Event            
Subsequent Event [Line Items]            
Unsatisfied performance obligation increase   $ 88,800,000        
Dividends declared (in dollars per share) $ 0.125          
Lease aggregate commitments         $ 2,400,000.0  
Subsequent Event | Equipment            
Subsequent Event [Line Items]            
Purchase obligation         9,600,000  
Air Charter Agreement | Infrastructure services | Subsequent Event            
Subsequent Event [Line Items]            
Purchase obligation         2,500,000  
Barge Chartering | Infrastructure services | Subsequent Event            
Subsequent Event [Line Items]            
Purchase obligation         2,100,000  
Housing Service Agreement | Infrastructure services | Subsequent Event            
Subsequent Event [Line Items]            
Purchase obligation         $ 600,000  
Revolving Credit Facility | Subsequent Event            
Subsequent Event [Line Items]            
Dividend pro forma excess availability, maximum, percent     22.50%      
Dividend payment after declaration term, maximum     60 days      
Scenario, Forecast            
Subsequent Event [Line Items]            
Dividends payable       $ 5,600,000