Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Service cost	$ 915	$ 949	$ 1,830	$ 1,898
Interest cost	2,075	1,993	4,151	3,986
Expected return on plan assets	(3,136)	(3,107)	(6,272)	(6,214)
Amortization of prior service cost	66	125	132	250
Amortization of net loss	16	(47)	31	(94)
Net periodic pension benefit	$ (64)	$ (87)	$ (128)	$ (174)