Recently Adopted Accounting Pronouncements - Additional Information (Details) - USD ($)	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ (424,448,411)	$ (427,951,923)	$ (427,164,813)
Other current assets	2,540,427	1,581,535	785,027
Unearned charter hire revenue	4,901,453	7,262,291	$ 5,678,673
Restricted cash		74,917		$ 74,917
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit		(787,110)
Other current assets	362,123	796,508
Unearned charter hire revenue	$ 192,019	$ 1,583,618