Note 6 - Accrued Retirement Benefits - Changes in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Thousands	1 Months Ended				12 Months Ended
	Nov. 30, 2022	Aug. 31, 2022	Nov. 30, 2021	Aug. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Change in benefit obligations:
Benefit obligations at beginning of year					$ 40,182	$ 54,655
Interest cost					1,034	1,237
Actuarial gain					(7,772)	(1,160)
Benefits paid					(16,907)	(14,550)
Benefit obligations at end of year					16,537	40,182
Change in plan assets:
Fair value of plan assets at beginning of year					32,103	43,587
Actual return on plan assets					(7,241)	1,384
Employer contributions		$ 5,700		$ 1,000	5,828	1,682
Benefits paid	$ (14,500)		$ (10,400)		(16,907)	(14,550)
Fair value of plan assets at end of year					13,783	32,103
Funded status					(2,754)	(8,079)
Accumulated benefit obligations					$ 16,537	$ 40,182