Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues, net	$ 69,391,315	$ 74,938,700	$ 146,780,912	$ 154,309,309
Voyage expenses	20,907,155	17,204,964	46,813,295	39,719,556
Vessel expenses	19,958,408	20,577,116	40,052,114	41,655,773
Charter hire expenses	11,179,480	10,108,258	22,671,386	20,376,322
Depreciation and amortization	9,761,322	9,272,460	19,168,430	18,548,875
General and administrative expenses	8,040,811	8,895,505	16,450,730	18,809,469
Gain on sale of vessels	(966,802)	(105,073)	(5,073,349)	(105,073)
Total operating expenses	68,880,374	65,953,230	140,082,606	139,004,922
Operating income	510,941	8,985,470	6,698,306	15,304,387
Interest expense	6,733,156	6,387,011	13,495,159	12,648,080
Interest income	(393,164)	(111,952)	(827,482)	(207,228)
Loss on debt extinguishment	0	0	2,268,452	0
Other expense/(income)	163,105	(740,356)	(2,275,150)	(639,977)
Total other expense, net	6,503,097	5,534,703	12,660,979	11,800,875
Net (loss)/income	$ (5,992,156)	$ 3,450,767	$ (5,962,673)	$ 3,503,512
Weighted average shares outstanding:
Basic (in shares)	71,348,524	70,515,320	71,316,093	70,484,240
Diluted (in shares)	71,348,524	72,086,980	71,316,093	71,560,775
Per share amounts:
Basic (loss)/income (in usd per share)	$ (0.08)	$ 0.05	$ (0.08)	$ 0.05
Diluted (loss)/income (in usd per share)	$ (0.08)	$ 0.05	$ (0.08)	$ 0.05