Revenues (Details) - USD ($)	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Revenues.
Net pool revenues—related party									$ 115,753,153	$ 202,918,232
Time charter revenues									49,474,510	38,737,172	$ 26,098,290
Voyage charter revenues									1,296,952	46,194,134	77,331,934
Other revenues									922,556	1,358,291	698,925
Total revenues	$ 47,585,174	$ 35,734,988	$ 33,611,233	$ 50,515,776	$ 85,335,229	$ 93,283,708	$ 74,946,432	$ 35,642,460	167,447,171	289,207,829	104,129,149
Profit-sharing sharing revenue									$ 0	$ 0	$ 7,800,000