Note 6 - Postretirement Benefit Plan (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Defined Benefit Plan, Benefit Obligation	$ 4,299,000		$ 4,299,000		$ 4,262,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 73,000	$ 65,000	$ 146,000	$ 130,000