Note 12 - Employee Benefit and Retirement Plans - Effect of 1% Change in Assumed Health Care Cost Trend Rates (Details) - USD ($) $ in Thousands	12 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Effect on postretirement benefit obligation	$ 1	$ 1	$ 1
Effect on postretirement benefit obligation	$ (1)	$ (1)	$ (1)

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration