Note 4 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Service cost	$ 915	$ 949
Interest cost	2,076	1,993
Expected return on plan assets	(3,136)	(3,107)
Amortization of prior service benefit	66	125
Amortization of net loss	15	(47)
Net periodic pension (benefit) cost	$ (64)	$ (87)