Recent Accounting Pronouncements - Operating Lease Assets and Liabilities (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 13,784,567		$ 13,784,567		$ 20,410,037	$ 20,410,037
Current portion of operating lease liabilities	12,511,790		12,511,790		13,255,978	13,255,978
Lease liabilities - long term	$ 2,441,982		$ 2,441,982		$ 8,301,793	8,301,793
Discount rate	5.48%		5.48%
Operating lease impairment	$ 352,368	$ 0	$ 352,368	$ 0
Minimum
Lessee, Lease, Description [Line Items]
Discount rate	5.05%		5.05%
Maximum
Lessee, Lease, Description [Line Items]
Discount rate	6.08%		6.08%
Weighted Average
Lessee, Lease, Description [Line Items]
Discount rate	5.50%		5.50%
Chartered-in contracts greater than 12 months
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 12,125,541		$ 12,125,541			18,442,965
Current portion of operating lease liabilities	11,853,335		11,853,335			12,622,524
Lease liabilities - long term	$ 1,441,411		$ 1,441,411			6,974,943
Discount rate	5.37%		5.37%
Office leases
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 1,659,026		$ 1,659,026			1,967,072
Current portion of operating lease liabilities	658,455		658,455			633,454
Lease liabilities - long term	$ 1,000,571		$ 1,000,571			$ 1,326,850
Discount rate	5.80%		5.80%