Vessels - Additional Information (Details)			3 Months Ended		9 Months Ended
	Mar. 23, 2018 USD ($)	Aug. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) vessel	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) vessel	Sep. 30, 2017 USD ($)	Sep. 04, 2018 order	Sep. 04, 2018 vessel	Sep. 04, 2018 USD ($)	Sep. 04, 2018 scrubber	Aug. 14, 2018 USD ($) vessel	Jul. 20, 2018 USD ($)	Dec. 19, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Number of vessels | vessel			46		46
Proceeds from sale of vessels					$ 20,545,202	$ 18,400,000
Gain on sale of vessels			$ 235,695	$ 202,487	340,768	$ 2,100,386
SDARI-64 Ultramax Dry Bulk Vessel
Property, Plant and Equipment [Line Items]
Vessel purchase price													$ 21,300,000
Vessel Avocet
Property, Plant and Equipment [Line Items]
Proceeds from sale of vessels		$ 9,600,000
Gain on sale of vessels			100,000		100,000
Vessel Thrush
Property, Plant and Equipment [Line Items]
Proceeds from sale of vessels	$ 10,800,000
Gain on sale of vessels			200,000
Ultramax Vessels
Property, Plant and Equipment [Line Items]
Vessel purchase price												$ 21,300,000
Advance payment for vessels					4,200,000
Ballast Water Treatment System
Property, Plant and Equipment [Line Items]
Number of vessels | vessel											46
Projected project costs											$ 500,000
System costs			300,000		300,000
Scrubber Systems
Property, Plant and Equipment [Line Items]
Number of vessels | vessel								19
Projected project costs									$ 2,000,000
Number of scrubbers | scrubber										19
Additional units to be purchased							18			18
System costs			$ 4,400,000		$ 4,400,000
Maximum | Scrubber Systems
Property, Plant and Equipment [Line Items]
Number of scrubbers | scrubber										37