Note 8 - Pension and Post-retirement Benefits - Net Periodic Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Pension Plan [Member]
Service cost
Interest cost	1,508	1,531	4,514	4,560
Expected return on plan assets	(1,286)	(1,300)	(3,849)	(3,876)
Amortization of net loss	5	5	19	17
Total	227	236	684	701
Post Retirement Medical Plan [Member]
Service cost	18	21	54	64
Interest cost	66	69	199	203
Amortization of net loss	7	24	22	74
Total	(43)	(20)	(128)	(62)
Amortization of prior service credit	$ (134)	$ (134)	$ (403)	$ (403)