Recent Accounting Pronouncements - Lease Expense (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lessee, Lease, Description [Line Items]
Sublease income from chartered-in contracts greater than 12 months *	$ 1,308,833	$ 1,353,020	$ 6,598,871	$ 7,194,837
Charter hire expenses
Lessee, Lease, Description [Line Items]
Lease expense for chartered-in contracts less than 12 months	2,560,224	7,977,490	6,348,081	24,022,456
Operating lease, expense	2,500,279	3,368,125	9,472,728	9,994,546
Lease cost	5,060,503	11,345,615	15,820,809	34,017,002
General and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease, expense	$ 185,525	$ 182,171	$ 548,349	$ 537,527