Note 12 - Employee Benefit and Retirement Plans - Status of the Postretirement Medical and Life Insurance Benefit Plan (Details) - USD ($)	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Amortization of net loss	$ (16,800,000)	$ (300,000)
U.S. Post Retirement Medical and Life Insurance Plan [Member]
Benefit obligation at beginning of year	6,930,000	6,385,000	$ 7,086,000
Service cost	73,000	72,000	85,000
Interest cost	240,000	265,000	270,000
Benefits paid	(329,000)	(346,000)	(388,000)
Actuarial (gain) loss	791,000	554,000	(668,000)
Benefit obligation at end of year	$ 7,705,000	$ 6,930,000	$ 6,385,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.73%	3.56%	4.27%
Rate of compensation increase	2.64%	2.64%	2.64%
Employer contributions	$ 329,000	$ 346,000	$ 388,000
Benefits paid	(329,000)	(346,000)	(388,000)
Fair value of plan assets at end of year
Current liability	(358,000)	(353,000)	(339,000)
Noncurrent liability	(7,347,000)	(6,577,000)	(6,046,000)
Net amount recognized in balance sheet	$ (7,705,000)	$ (6,930,000)	$ (6,385,000)
Discount rate	3.56%	4.27%	3.92%
Rate of compensation increase	2.64%	2.64%	2.64%
Prior service credit	$ 2,240,000	$ 2,777,000	$ 3,314,000
Accumulated loss	(2,160,000)	(1,452,000)	(928,000)
Amounts not yet recognized as a component of net periodic benefit cost	80,000	1,325,000	2,386,000
Accumulated net periodic benefit cost in excess of contributions	(7,785,000)	(8,255,000)	(8,771,000)
Amortization of prior service credit	(537,000)	(537,000)	(537,000)
Amortization of net loss	83,000	30,000	99,000
Net periodic benefit cost	(141,000)	(170,000)	(83,000)
Prior service credit	537,000	537,000	537,000
Net loss	(166,000)	(83,000)	(30,000)
Defined Benefit Plan, Expected Amortization, Next Fiscal Year, Total	$ 371,000	$ 454,000	$ 507,000
Healthcare cost trend rate assumed for next year		6.60%	6.60%
Rate to which the cost trend rate gradually declines		4.50%	4.50%
Year that the rate reaches the rate at which it is assumed to remain		2037	2037