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Derivative Instruments and Fair Value Measurements (Details Textual)
3 Months Ended 6 Months Ended
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Derivative, Number of Instruments Held | swap           1
Interest Rate Swap [Member]            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Fixed Interest Rate           6.63%
Forward Contracts [Member]            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Derivative gain (loss) $ 1,650,000   $ (1,075,000)      
Swap [Member]            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Derivative gain (loss) (173,000) $ (1,265,000) 585,000 $ (948,000)    
Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Fair Value, Net Asset (Liability)   $ (104,000)   $ (104,000)    
Fair Value, Measurements, Recurring [Member] | Forward Contracts [Member]            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Fair Value, Net Asset (Liability) 1,053,975   1,053,975   $ (20,950)  
Fair Value, Measurements, Recurring [Member] | Swap [Member] | Fuel [Member]            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Fair Value, Net Asset (Liability) $ (281,142)   $ (281,142)   $ 303,675