Pension and Other Postretirement Benefits - Components of Net Periodic Other Postretirement Benefit Cost (Details) - Other postretirement benefit plans [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Net periodic other postretirement benefit costs
Interest cost	$ 153	$ 157	$ 460	$ 471
Amortization of prior service credit	(22)	(6)	(68)	(16)
Recognition of actuarial loss	62	70	186	210
Net periodic other postretirement benefit cost	$ 193	$ 221	$ 578	$ 665