Note 6 - Pension and Other Postretirement Benefits - Components of net Periodic Benefit Cost (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Pension Plan [Member]
Service cost		$ 502	$ 530
Interest cost		669	635
Expected return on plan assets		(839)	(657)
Amortization of prior service cost		0	0
Recognized actuarial loss (gain)		331	301
Net periodic benefit cost (a)	[1]	663	809
Postemployment Retirement Benefits [Member]
Service cost		212	208
Interest cost		286	299
Expected return on plan assets		0	0
Amortization of prior service cost		0	(248)
Recognized actuarial loss (gain)		(8)	(9)
Net periodic benefit cost (a)	[1]	$ 490	$ 250

[1] The components of net periodic cost other than the service cost component are included in Other income (expense), net in the Consolidated Statements of Income.