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Summary of Significant Accounting Policies - Additional Information (Detail)
 3 Months Ended
Mar. 31, 2017
USD ($)
Customer
Segment
Mar. 31, 2016
USD ($)
Dec. 31, 2016
USD ($)
Significant Accounting Policies [Line Items]      
Number of customers with supply agreement | Customer 4    
Agreements expiring period 2019    
Agreements expiring period 2020    
Rail car revenue recognized $ 1,683,000 $ 1,553,000  
Reservation revenue recognized 7,500,000 2,769,000  
Amount related to minimum commitments under customer contracts due or payable $ 0   $ 0
Accounts receivables due period 30 days    
Accounts receivables, allowance for doubtful accounts $ 0   0
Deferred revenue balance 0   1,615,000
Revenue generated from transportation 6,604,000 0  
Cost of goods sold generated from shipping 7,302,000 0  
Inventory write-down 0 0  
Amortization of deferred financing cost 106,000 37,000  
Accretion of debt discount costs 0 74,000  
Recognized income tax interest and penalties 0    
Probable environmental matters $ 0   0
Number of operating segment | Segment 1    
Revolving Credit Facility      
Significant Accounting Policies [Line Items]      
Long-term Line of Credit $ 0   $ 0
Take-or-pay Contracts [Member]      
Significant Accounting Policies [Line Items]      
Revenue recognized for shortfall payments relating to minimum commitments $ 0 $ 2,997,000