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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 |

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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