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Derivative Instruments and Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - USD ($)
Jun. 30, 2017
Dec. 31, 2016
Margin Accounts [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, net asset (liability) $ (756,026) $ (488,084)
Forward Contracts [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, net asset (liability) (1,053,975) 20,950
Fuel Swap Contracts [Member] | Fuel [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, net asset (liability) 281,142 (303,675)
Fair Value, Inputs, Level 1 [Member] | Margin Accounts [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, net asset (liability) (756,026) (488,084)
Fair Value, Inputs, Level 2 [Member] | Forward Contracts [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, net asset (liability) (1,053,975) (20,950)
Fair Value, Inputs, Level 2 [Member] | Fuel Swap Contracts [Member] | Fuel [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value, net asset (liability) $ 281,142 $ (303,675)