Note 9 - Pension and Post-retirement Benefits - Net Periodic Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Pension Plan [Member]
Service cost
Interest cost	1,362	1,508	4,077	4,515
Expected return on plan assets	(1,305)	(1,286)	(3,908)	(3,849)
Amortization of net loss	9	5	28	19
Total	66	227	198	684
Post Retirement Medical Plan [Member]
Service cost	18	18	55	54
Interest cost	60	66	180	199
Amortization of net loss	20	7	62	22
Total	(36)	(43)	(106)	(128)
Amortization of prior service credit	$ (134)	$ (134)	$ (403)	$ (403)