Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Service cost	$ 914	$ 949	$ 2,744	$ 2,847
Interest cost	2,076	1,993	6,227	5,979
Expected return on plan assets	(3,136)	(3,107)	(9,408)	(9,321)
Amortization of prior service cost	67	125	199	375
Amortization of net loss	15	(47)	46	(141)
Net periodic pension benefit	$ (64)	$ (87)	$ (192)	$ (261)