Note 3 - Vessel Acquisitions and Dispositions - Vessels Under Construction (Details) - Subsequent Event [Member] $ in Millions	Apr. 18, 2016 USD ($) Boe T
Americas [Member] | Large Platform Supply Vessel One [Member] | BAE Systems [Member]
Vessels Under Construction, Length	286
Vessels Under Construction, Brake Horsepower | Boe	10,960	[1]
Vessels Under Construction, Deadweight Tons | T	5,300	[2]
Vessels Under Construction, Expected Cost | $	$ 48
North Sea [Member] | Large Platform Supply Vessel [Member] | Simek [Member]
Vessels Under Construction, Length	304
Vessels Under Construction, Brake Horsepower | Boe	11,935	[1]
Vessels Under Construction, Deadweight Tons | T	4,700	[2]
Vessels Under Construction, Expected Cost | $	$ 60

[1] BHP - Brake Horsepower

[2] DWT - Deadweight Tons