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Revenue - Additional information (Details)
$ in Millions
 3 Months Ended
Mar. 31, 2018
USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]  
Remaining performance obligation $ 13.3
Petroleum | Minimum  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]  
Payment terms 2 days
Petroleum | Maximum  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]  
Payment terms 32 days
Nitrogen Fertilizer | Minimum  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]  
Payment terms 15 days
Nitrogen Fertilizer | Maximum  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]  
Payment terms 30 days