Significant Accounting Policies - Lease Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sub lease income from chartered-in contracts greater than 12 months *	$ 8,589,156	$ 10,259,768
Charter hire expenses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease expense for chartered-in contracts less than 12 months	8,731,978	28,805,970
Operating lease, expense	12,548,246	13,362,672
Lease cost	21,280,224	42,168,642
General and administrative expenses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, expense	$ 733,874	$ 719,698