Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenues, net	$ 74,938,700	$ 53,631,224	$ 154,309,309	$ 99,486,281
Voyage expenses	17,204,964	13,379,664	39,719,556	26,733,011
Vessel expenses	20,577,116	19,308,802	41,655,773	37,264,321
Charter hire expenses	10,108,258	6,445,580	20,376,322	10,318,912
Depreciation and amortization	9,272,460	8,020,597	18,548,875	15,513,405
General and administrative expenses	8,895,505	8,589,979	18,809,469	16,368,800
Gain on sale of vessels	(105,073)	(1,805,785)	(105,073)	(1,897,899)
Total operating expenses	65,953,230	53,938,837	139,004,922	104,300,550
Operating income/(loss)	8,985,470	(307,613)	15,304,387	(4,814,269)
Interest expense	6,387,011	6,858,716	12,648,080	13,303,747
Interest income	(111,952)	(185,641)	(207,228)	(375,439)
Other income	(740,356)	(1,092,222)	(639,977)	(785,663)
Total other expense, net	5,534,703	5,580,853	11,800,875	12,142,645
Net income/(loss)	$ 3,450,767	$ (5,888,466)	$ 3,503,512	$ (16,956,914)
Weighted average shares outstanding:
Basic (in shares)	70,515,320	70,329,050	70,484,240	67,996,330
Diluted (in shares)	72,086,980	70,329,050	71,560,775	67,996,330
Per share amounts:
Basic income/(loss) (in dollars per share)	$ 0.05	$ (0.08)	$ 0.05	$ (0.25)
Diluted income/(loss) (in dollars per share)	$ 0.05	$ (0.08)	$ 0.05	$ (0.25)