Retirement Benefits - Other postretirement benefit plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Amounts recognized on the Consolidated Balance Sheet
Pensions and other postretirement benefits	$ (1,406,082)	$ (2,076,143)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Expense related to other postretirement benefits	4,357	8,754	$ 4,340
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	89,785	75,953
Service cost	469	591
Interest cost	1,922	2,834
Acquisition	291	0
Special termination cost	0	4,521
Actuarial (gain) loss	(8,235)	10,217
Benefits paid	(4,299)	(4,331)
Benefit obligation at end of year	79,933	89,785	$ 75,953
Funded status	(79,933)	(89,785)
Amounts recognized on the Consolidated Balance Sheet
Other accrued liabilities	(6,532)	(6,216)
Pensions and other postretirement benefits	(73,401)	(83,569)
Net amount recognized	(79,933)	(89,785)
Amounts recognized in Accumulated Other Comprehensive (Loss)
Net actuarial loss	12,828	22,914
Prior service (credit)	(435)	(556)
Net amount recognized	12,393	$ 22,358
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) 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	1,095
Estimated amount of prior service credit that will be amortized from accumulated other comprehensive (loss) income into net periodic postretirement cost	$ (121)