Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues, net	$ 71,486,350	$ 74,110,376	$ 69,391,315	$ 77,389,597	$ 86,692,209	$ 69,092,740	$ 74,938,700	$ 79,370,609	$ 292,377,638	$ 310,094,258	$ 236,784,625
Time charters
Disaggregation of Revenue [Line Items]
Revenues, net									128,142,708	140,006,570
Voyage charters
Disaggregation of Revenue [Line Items]
Revenues, net									$ 164,234,930	$ 170,087,688