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Summary of Significant Accounting Policies - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2016
USD ($)
Customer
Segment
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 18, 2015
USD ($)
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 $ 5,732,000 $ 3,543,000 $ 1,563,000  
Reservation revenue recognized 15,041,000 1,000,000 0  
Amount related to minimum commitments under customer contracts due or payable $ 0 0 0  
Accounts receivables due period 30 days      
Accounts receivables, allowance for doubtful accounts $ 0 0    
Deferred revenue balance 1,615,000 7,133,000    
Revenue generated from shipping 480,000 2,294,000 3,972,000  
Cost of goods sold generated from shipping 1,172,000 2,257,000 4,246,000  
Inventory write-down 0      
Debt, face amount 1,178,000 486,000    
Amortization of deferred financing cost 159,000 251,000 86,000  
Accretion expense of debt discount 263,000 519,000 183,000  
Accelerated amortization of debt issuance costs 18,000      
Recognized income tax interest and penalties 0      
Probable environmental matters $ 0      
Number of operating segment | Segment 1      
Revolving Credit Facility        
Significant Accounting Policies [Line Items]        
Long-term Line of Credit $ 0     $ 75,000,000
Unbilled Revenues [Member]        
Significant Accounting Policies [Line Items]        
Deferred revenue 0 3,875,000    
Take-or-pay Contracts [Member]        
Significant Accounting Policies [Line Items]        
Revenue recognized relating to minimum required payments $ 20,902,000 $ 10,095,000 $ 0