Commitments and Contingencies (Details) $ in Millions			1 Months Ended
	May 10, 2017 USD ($) t $ / d	Apr. 28, 2017 t $ / d	Oct. 31, 2014 t $ / d	Sep. 30, 2017 USD ($) t
Property, Plant and Equipment [Line Items]
Dead weight tonnage of operating fleet | t				2,737,100
Japanese Vessel
Property, Plant and Equipment [Line Items]
Dead weight tonnage of operating fleet | t			37,000
Charters agreement term			7 years
Charters agreement term, extension option			1 year
Vessel agreement, termination fee | $	$ 1.5			$ 1.5
Japanese Vessel | First Seven Years
Property, Plant and Equipment [Line Items]
Vessel hiring rate (in dollars per day)			13,500
Japanese Vessel | Eighth Year Option
Property, Plant and Equipment [Line Items]
Vessel hiring rate (in dollars per day)			13,750
2013 Built Japanese Vessel
Property, Plant and Equipment [Line Items]
Dead weight tonnage of operating fleet | t	61,400	61,400
Charters agreement term	4 years	4 years
Charters agreement term, extension option	2 years	2 years
Vessel hiring rate (in dollars per day)		12,800
2013 Built Japanese Vessel | First Four Years
Property, Plant and Equipment [Line Items]
Vessel hiring rate (in dollars per day)	12,800
2013 Built Japanese Vessel | First Optional Year
Property, Plant and Equipment [Line Items]
Vessel hiring rate (in dollars per day)		13,800
2013 Built Japanese Vessel | Second Optional Year
Property, Plant and Equipment [Line Items]
Vessel hiring rate (in dollars per day)		14,300