Retirement Benefits - Assumptions used to measure benefit obligations (Details) - Pension Plans, Defined Benefit	Jun. 30, 2018	Jun. 30, 2017
U.S. defined benefit plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.01%	3.64%
Average increase in compensation	3.65%	3.89%
Non-U.S. defined benefit plans | Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	0.30%	0.30%
Average increase in compensation	1.75%	2.00%
Non-U.S. defined benefit plans | Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.37%	7.57%
Average increase in compensation	5.50%	5.50%