Note 6 - Accrued Retirement Benefits (Details Textual) $ in Thousands	1 Months Ended		12 Months Ended
	Nov. 30, 2021 USD ($)	Aug. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jan. 31, 2021 USD ($)
Defined Benefit Plan, Number of People Receiving Pension Benefits	384
Defined Benefit Plan, Plan Assets, Benefits Paid	$ 10,400		$ 14,550	$ 4,694
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax			15,600	21,700
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year					$ 600
Defined Benefit Plan, Plan Assets, Contributions by Employer		$ 1,000	$ 1,682	$ 128