Note 10 - Retirement Plans - Plan Assets (Details)	Mar. 31, 2021	Mar. 31, 2020
Target Allocation	100.00%
Percentage of Plan Assets	100.00%	100.00%
Defined Benefit Plan, Equity Securities [Member]
Target Allocation	50.00%
Percentage of Plan Assets	48.00%	97.00%
Defined Benefit Plan, Debt Security [Member]
Target Allocation	50.00%
Percentage of Plan Assets	50.00%	0.00%
Defined Benefit Plan, Real Estate [Member]
Target Allocation	0.00%
Percentage of Plan Assets	0.00%	0.00%
Defined Benefit Plan, Cash [Member]
Target Allocation	0.00%
Percentage of Plan Assets	2.00%	3.00%

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

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