Note 4 - Vessel Acquisitions and Dispositions - Vessels Disposed (Details) - Americas [Member] - Vessel [Member]	6 Months Ended
	Jun. 30, 2017 Boe T
Mako [Member]
Vessel Disposals, Year Built	2008
Vessel Disposals, Length	181
Vessel Disposals, Brake Horsepower (Barrel of Oil Equivalent) | Boe	7,200	[1]
Vessel Disposals, Deadweight Tons (US Ton) | T	552	[2]
Tiger [Member]
Vessel Disposals, Year Built	2009
Vessel Disposals, Length	181
Vessel Disposals, Brake Horsepower (Barrel of Oil Equivalent) | Boe	7,200	[1]
Vessel Disposals, Deadweight Tons (US Ton) | T	552	[2]

[1] BHP - Brake Horsepower

[2] DWT - Deadweight Tons