Vessels, Net (Details)	3 Months Ended
	Jun. 30, 2019 USD ($) item	Mar. 31, 2019 USD ($)
Accumulated depreciation
Vessels, net	$ 1,463,827,783	$ 1,478,520,314
The number of vessels with contracts to purchase exhaust gas cleaning systems | item	10
Vessels
Cost
Balance at the beginning of the period	$ 1,732,993,810
Other additions	1,414,195
Balance at the end of the period	1,734,408,005
Accumulated depreciation
Balance at the beginning of the period	(254,473,496)
Impairment	0
Depreciation	(16,106,726)
Balance at the end of the period	$ (270,580,222)
The number of vessels with contracts to purchase exhaust gas cleaning systems | item	10
Mortgaged VLGC vessels, carrying value	$ 1,463,800,000	$ 1,478,500,000