Derivative Instruments and Fair Value Measurements - Derivative Instruments Not Designated As Hedging Instruments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, location of (gain)/loss recognized	$ (740,356)	$ (1,092,222)	$ (639,977)	$ (785,663)
FFAs | Other current assets
Derivative Instruments, Gain (Loss) [Line Items]
Collateral related to derivative instruments under collateral security arrangements	891,344		891,344		$ 178,836
FFAs | Derivatives not designated as hedging instruments | Fair value of derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, balance sheet location, fair value of derivatives	461,993		461,993		73,170
FFAs | Derivatives not designated as hedging instruments | Other current assets
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, balance sheet location, total	117,360		117,360		0
FFAs | Other income | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, location of (gain)/loss recognized	36,625	(1,049,363)	82,432	(788,715)
Bunker Swaps | Derivatives not designated as hedging instruments | Other current assets
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, balance sheet location, total	635,258		635,258		$ 128,845
Bunker Swaps | Other income | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, location of (gain)/loss recognized	$ (776,981)	$ (42,859)	$ (722,409)	$ 3,052