Recent Accounting Pronouncements - Lease Expense (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Sub lease income from chartered-in contracts greater than 12 months *	$ 3,997,224	$ 3,082,752
Charter hire expenses
Lessee, Lease, Description [Line Items]
Lease expense for chartered-in contracts less than 12 months	2,748,414	8,360,743
Operating lease, expense	3,292,525	3,131,163
Lease cost	6,040,939	11,491,906
General and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease, expense	$ 181,412	$ 178,000