Basis of Presentation and Significant Accounting Policies - Advance Hire, Prepaid Expenses and Other Current Assets (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Advance hire	$ 4,462,379	$ 3,985,826
Prepaid expenses	2,813,696	4,924,557
Accrued receivables	3,869,769	6,466,068
Margin deposit	2,023,596	269,379
Other current assets	2,406,002	3,124,995
Advance hire, prepaid expenses and other current assets	$ 15,575,442	$ 18,770,825