Significant Accounting Policies - Schedule of Effects of ASC 606 (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable	$ 19,785,582				$ 17,246,540				$ 19,785,582	$ 17,246,540		$ 16,320,557
Other current assets	2,246,740				785,027				2,246,740	785,027		1,581,535
Unearned charter hire revenue	6,926,839				5,678,673				6,926,839	5,678,673		6,336,308
Revenues, net	86,692,209	$ 69,092,740	$ 74,938,700	$ 79,370,609	74,587,441	$ 62,710,903	$ 53,631,224	$ 45,855,057	310,094,258	236,784,625	$ 124,492,844
Voyage expenses									79,566,452	62,351,252	42,093,714
Charter hire expenses									38,045,778	31,283,956	12,845,468
Net income/(loss)	$ 6,486,350	$ 2,584,822	$ 3,450,767	$ 52,745	$ (16,584,425)	$ (10,255,346)	$ (5,888,466)	$ (11,068,448)	$ 12,574,684	$ (43,796,685)	$ (223,522,435)
Basic income (in dollars per share)	$ 0.09	$ 0.04	$ 0.05	$ 0.00	$ (0.24)	$ (0.15)	$ (0.08)	$ (0.17)	$ 0.18	$ (0.63)	$ (10.87)
Diluted net income (in dollars per share)	$ 0.09	$ 0.04	$ 0.05	$ 0.00	$ (0.24)	$ (0.15)	$ (0.08)	$ (0.17)	$ 0.18	$ (0.63)	$ (10.87)
Accumulated deficit	$ (415,377,239)				$ (427,164,813)				$ (415,377,239)	$ (427,164,813)		(427,951,923)
Calculated under Revenue Guidance in Effect before Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable	20,771,299				17,246,540				20,771,299	17,246,540
Other current assets	1,478,450				785,027				1,478,450	785,027
Unearned charter hire revenue	6,528,275				5,678,673				6,528,275	5,678,673
Revenues, net									309,894,921
Voyage expenses									79,292,962
Charter hire expenses									37,957,027
Net income/(loss)									$ 12,737,588
Basic income (in dollars per share)									$ 0.18
Diluted net income (in dollars per share)									$ 0.18
Accumulated deficit					(427,164,813)					(427,164,813)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable	(985,717)				(925,983)				$ (985,717)	(925,983)
Other current assets	768,290				796,508				768,290	796,508		800,000
Unearned charter hire revenue	$ 398,564				657,635				398,564	657,635		1,600,000
Revenues, net									199,337
Voyage expenses									273,490
Charter hire expenses									88,751
Net income/(loss)									$ (162,904)
Basic income (in dollars per share)									$ 0.00
Diluted net income (in dollars per share)									$ 0.00
Accumulated deficit					$ (787,110)					$ (787,110)		$ (800,000)