Note 8 - Assets Held for Sale, Asset Sales and Asset Impairments (Details Textual) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020
Number of Vessels, Held for Sale, Addition			3	7	88
Number of Vessels Sold		7	12	9
Number of Vessels, Transfer from Held for Sale to Active Fleet		8	1	3
Number of Vessels, Held for Sale		0	8	18
Number of Active Vessels Sold				10
Proceeds from Sale of Productive Assets, Total		$ 15,506	$ 13,568	$ 34,010
Proceeds from Sale of Vessels and Other Assets		15,500	13,600	34,000
Impairment of Long-Lived Assets to be Disposed of				13,700
Impairment Charge Recaptured			500	1,700
Asset Impairment Charges, Total		0	714	15,643
Vessel, Obsolete Inventory [Member]
Asset Impairment Charges, Total		$ 0	$ 1,200	$ 1,900
Third-party Operator, Family Member of Director [Member]
Proceeds from Sale of Productive Assets, Total	$ 11,400
Gain (Loss) on Sale of Assets and Asset Impairment Charges	$ 4,300