Retirement Benefits - Other postretirement benefit plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Amounts recognized on the Consolidated Balance Sheet
Pensions and other postretirement benefits	$ (1,177,605)	$ (1,406,082)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Expense related to other postretirement benefits	2,755	4,357	$ 8,754
Special termination cost			4,521
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	79,933	89,785
Service cost	320	469
Interest cost	2,003	1,922
Acquisition	0	291
Actuarial gain	(11,259)	(8,235)
Benefits paid	(4,476)	(4,299)
Benefit obligation at end of year	66,521	79,933	$ 89,785
Funded status	(66,521)	(79,933)
Amounts recognized on the Consolidated Balance Sheet
Other accrued liabilities	(6,180)	(6,532)
Pensions and other postretirement benefits	(60,341)	(73,401)
Net amount recognized	(66,521)	(79,933)
Amounts recognized in Accumulated Other Comprehensive (Loss)
Net actuarial loss	1,232	12,828
Prior service credit	(314)	(435)
Net amount recognized	918	$ 12,393
Defined Benefit Plan, Expected Amortization, Next Fiscal Year [Abstract]
Estimated amount of net actuarial loss that will be amortized from accumulated other comprehensive (loss) income into net periodic postretirement cost	14
Estimated amount of prior service credit that will be amortized from accumulated other comprehensive (loss) income into net periodic postretirement cost	$ (121)