Recently Adopted Accounting Pronouncements - Schedule of Effects of ASC 606 (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable	$ 13,976,108			$ 17,246,540
Other current assets	1,577,556		$ 1,581,535	785,027
Unearned charter hire revenue	6,231,209		7,262,291	5,678,673
Other accrued liabilities	5,984,737			11,810,366
Income Statement [Abstract]
Revenues, net	79,370,609	$ 45,855,057
Voyage expenses	22,514,592	13,353,347
Charter hire expenses	10,268,064	3,873,332
Net income/(loss)	$ 52,745	$ (11,068,448)
Basic income/(loss) per share (in dollars per share)	$ 0.00	$ (0.17)
Diluted income (loss) per share (in dollars per share)	$ 0.00	$ (0.17)
Statement of Cash Flows [Abstract]
Accounts receivable	$ 3,270,432	$ (3,676,803)
Unearned revenue	(1,031,082)	1,114,886
Other current and non-current assets	(121,954)	(426,860)
Other accrued and other non-current liabilities	(5,009,784)	$ (3,738,154)
Accumulated deficit	(427,899,178)		(427,951,923)	(427,164,813)
Calculated under Revenue Guidance in Effect before Topic 606
Statement of Financial Position [Abstract]
Accounts receivable	14,531,212
Other current assets	1,055,071			785,027
Unearned charter hire revenue	6,950,116			5,678,673
Other accrued liabilities	5,961,064
Income Statement [Abstract]
Revenues, net	78,533,776
Voyage expenses	22,268,705
Charter hire expenses	10,032,395
Net income/(loss)	$ (302,532)
Basic income/(loss) per share (in dollars per share)	$ 0.00
Diluted income (loss) per share (in dollars per share)	$ 0.00
Statement of Cash Flows [Abstract]
Accumulated deficit				$ (427,164,813)
Calculated under Revenue Guidance in Effect before Topic 606 | Bunker Expenses
Statement of Financial Position [Abstract]
Other current assets			600,000
Calculated under Revenue Guidance in Effect before Topic 606 | Charter Hire Expenses
Statement of Financial Position [Abstract]
Other current assets			200,000
Calculated under Revenue Guidance in Effect before Topic 606 | Voyage In Progress
Statement of Financial Position [Abstract]
Unearned charter hire revenue			1,500,000
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Statement of Financial Position [Abstract]
Accounts receivable	$ (555,104)
Other current assets	522,485		796,508
Unearned charter hire revenue	718,907		1,583,618
Other accrued liabilities	(23,673)
Income Statement [Abstract]
Revenues, net	836,833
Voyage expenses	(245,887)
Charter hire expenses	(235,669)
Net income/(loss)	$ 355,277
Basic income/(loss) per share (in dollars per share)	$ 0.01
Diluted income (loss) per share (in dollars per share)	$ 0.00
Statement of Cash Flows [Abstract]
Accumulated deficit			$ (787,110)