Employee Benefit Plans - Components of Net Periodic Benefit Cost and Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Pension Plan
Components of net periodic benefit cost
Service cost	$ 0	$ 0
Interest cost	1,059	1,426
Expected return on plan assets	(1,102)	(1,485)
Amortization of net loss (gain)	370	370
Net periodic benefit (credit) cost	$ 327	$ 311
Weighted average assumptions used to determine benefit obligations
Discount rate	3.45%	3.45%
Expected long-term return on plan assets	6.75%	6.75%
Other Postretirement Benefit Plan
Components of net periodic benefit cost
Service cost	$ 147	$ 133
Interest cost	214	222
Amortization of net loss (gain)	(125)	(209)
Net periodic benefit (credit) cost	$ (156)	$ (293)
Retiree Medical Plan
Weighted average assumptions used to determine benefit obligations
Discount rate	3.62%	4.25%
Death Benefit Plan
Weighted average assumptions used to determine benefit obligations
Discount rate	3.64%	4.25%