Vessels, Net (Details)	9 Months Ended
	Dec. 31, 2018 USD ($) item	Mar. 31, 2018 USD ($)
Accumulated depreciation
Vessels, net	$ 1,493,150,911	$ 1,539,111,833
The number of vessels with contracts to purchase exhaust gas cleaning systems | item	10
Vessels
Cost
Balance at the beginning of the period	$ 1,728,987,980
Other additions	2,706,699
Balance at the end of the period	1,731,694,679
Accumulated depreciation
Balance at the beginning of the period	(189,876,147)
Impairment	0
Depreciation	(48,667,621)
Balance at the end of the period	$ (238,543,768)
The number of vessels with contracts to purchase exhaust gas cleaning systems | item	10
Mortgaged VLGC vessels, carrying value	$ 1,493,200,000	$ 1,539,100,000