Note 6 - Accrued Retirement Benefits - Summary of Assumptions Used (Details)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Expected long-term return on plan assets	4.50%	4.75%
Minimum [Member]
Discount rate	2.28%	3.10%
Maximum [Member]
Discount rate	2.35%	3.14%

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2919-114920

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Balance Type:	na
Period Type:	duration