Retirement Benefits - Other postretirement benefit plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Amounts recognized on the Consolidated Balance Sheet
Pensions and other postretirement benefits	$ (1,304,379)	$ (1,177,605)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Expense related to other postretirement benefits	1,838	2,755	$ 4,357
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	66,521	79,933
Service cost	205	320
Interest cost	2,043	2,003
Actuarial loss (gain)	(3,235)	(11,259)
Benefits paid	(4,536)	(4,476)
Benefit obligation at end of year	60,998	66,521	$ 79,933
Funded status	(60,998)	(66,521)
Amounts recognized on the Consolidated Balance Sheet
Other accrued liabilities	(5,308)	(6,180)
Pensions and other postretirement benefits	(55,690)	(60,341)
Net amount recognized	(60,998)	(66,521)
Amounts recognized in Accumulated Other Comprehensive (Loss)
Net actuarial loss	(1,713)	1,232
Prior service credit	(194)	(314)
Net amount recognized	$ (1,907)	$ 918