Note 6 - Postretirement Benefit Plan (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Defined Benefit Plan, Benefit Obligation	$ 4,307,000		$ 4,307,000		$ 4,262,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 74,000	$ 65,000	$ 220,000	$ 195,000