Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenues, net	$ 79,370,609	$ 45,855,057
Voyage expenses	22,514,592	13,353,347
Vessel expenses	21,078,657	17,955,519
Charter hire expenses	10,268,064	3,873,332
Depreciation and amortization	9,276,415	7,492,808
General and administrative expenses	9,913,964	7,778,821
Gain on sale of vessel	0	(92,114)
Total operating expenses	73,051,692	50,361,713
Operating income/(loss)	6,318,917	(4,506,656)
Interest expense	6,261,069	6,445,031
Interest income	(95,276)	(189,798)
Other expense	100,379	306,559
Total other expense, net	6,266,172	6,561,792
Net income/(loss)	$ 52,745	$ (11,068,448)
Weighted average shares outstanding:
Basic (in shares)	70,452,814	65,637,692
Diluted (in shares)	71,531,864	65,637,692
Per share amounts:
Basic income/(loss) (in dollars per share)	$ 0.00	$ (0.17)
Diluted income/(loss) (in dollars per share)	$ 0.00	$ (0.17)