Note 3 - Revenue Recognition (Details Textual) - Vessel [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Contract with Customer, Liability, Revenue Recognized	$ 2.2
Other Current Assets [Member]
Contract with Customer, Asset, after Allowance for Credit Loss, Current	5.4	$ 4.7
Other Assets [Member]
Contract with Customer, Asset, after Allowance for Credit Loss, Current	2.9	$ 4.3
Other Current Liabilities [Member]
Contract with Customer, Liability, Current	5.0
Other Liabilities [Member]
Contract with Customer, Liability, Noncurrent	$ 1.8