Note 2 - Summary of Significant Accounting Policies - Property and Equipment, Net (Details)	12 Months Ended
	Dec. 31, 2019
Vessels and Vessel Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)	15 years
Vessels and Vessel Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)	25 years
Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life (Year)	5 years
Computer Hardware and Software [Member]
Property, Plant and Equipment, Useful Life (Year)	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment, Estimated Useful Lives	Shorter of lease term or related asset life