Subsequent Events (Details)	May 04, 2018 t $ / d	Mar. 31, 2018 t
Subsequent Event [Line Items]
Dead weight tonnage of operating fleet | t		2,746,891
Ultramax Vessels | Subsequent Event
Subsequent Event [Line Items]
Dead weight tonnage of operating fleet | t	61,425
Charters agreement term	3 years
Charters agreement term, extension option	2 years
Vessel hiring rate (in dollars per day)	12,700
First Optional Year | Ultramax Vessels | Subsequent Event
Subsequent Event [Line Items]
Vessel hiring rate (in dollars per day)	13,750
Second Optional Year | Ultramax Vessels | Subsequent Event
Subsequent Event [Line Items]
Vessel hiring rate (in dollars per day)	14,750