Note 6 - Employee Benefit Plans - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan [Abstract]
Service cost	$ 3,659	$ 3,794	$ 6,262
Interest cost	8,302	7,974	5,476
Expected return on plan assets	$ (12,544)	$ (12,428)	$ (13,452)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Comprehensive Income (Loss), Net of Tax, Attributable to Parent	Comprehensive Income (Loss), Net of Tax, Attributable to Parent	Comprehensive Income (Loss), Net of Tax, Attributable to Parent
Amortization of prior service benefit	$ 265	$ 500	$ 511
Amortization of net loss (gain)	61	(188)	2,049
Net periodic pension (benefit) cost	$ (257)	$ (348)	$ 846