Note 3 - Vessel Acquisitions and Dispositions - Vessels Disposed (Details) - Large Platform Supply Vessel [Member] - North Sea [Member]	9 Months Ended
	Sep. 30, 2015 Boe g
North Truck [Member]
Vessels Disposed, Year Built	1983
Vessels Disposed, Length	265
Vessels Disposed, Brake Horsepower | Boe	6,120	[1]
Vessels Disposed, Deadweight Tons	3,370	[2]
Highland Trader [Member]
Vessels Disposed, Year Built	1996
Vessels Disposed, Length	220
Vessels Disposed, Brake Horsepower | Boe	5,450	[1]
Vessels Disposed, Deadweight Tons	3,115	[2]

[1] BHP - Brake Horsepower

[2] DWT - Deadweight Tons