Note 3 - Vessel Acquisitions and Dispositions - Vessels Disposed (Details)	6 Months Ended
	Jun. 30, 2016 Boe T
North Sea [Member] | Special Purpose Vessel [Member] | Highland Spirit [Member]
Vessels Additions, Year Built	1998
Vessels Additions, Length	202
Vessels Additions, Brake Horsepower | Boe	6,000	[1]
Vessels Additions, Deadweight Tons | T	1,620	[2]
South East Asia [Member] | Small Anchor Handler [Member] | Sea Intrepid [Member]
Vessels Additions, Year Built	2005
Vessels Additions, Length	193
Vessels Additions, Brake Horsepower | Boe	5,150	[1]
Vessels Additions, Deadweight Tons | T	1,500	[2]
South East Asia [Member] | Small Anchor Handler [Member] | Sea Guardian [Member]
Vessels Additions, Year Built	2006
Vessels Additions, Length	193
Vessels Additions, Brake Horsepower | Boe	5,150	[1]
Vessels Additions, Deadweight Tons | T	1,500	[2]

[1] BHP - Brake Horsepower

[2] DWT - Deadweight Tons