Pension and Other Postretirement Benefits - Schedule of Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 9.5	$ 20.5	$ 31.2
Interest cost	52.1	50.3	58.0
Expected return on plan assets	(65.9)	(65.1)	(66.1)
Amortization of net loss	13.5	37.8	27.4
Amortization of prior service cost (benefit)	2.1	1.8	0.4
Curtailment loss	0.0	0.5	0.0
Net periodic benefit costs	11.3	45.8	50.9
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2.6	3.6	3.3
Interest cost	9.5	9.2	10.4
Expected return on plan assets	(6.9)	(6.9)	(7.0)
Amortization of net loss	2.9	3.2	2.7
Amortization of prior service cost (benefit)	(5.2)	(6.5)	(6.5)
Curtailment loss	0.0	0.0	0.0
Net periodic benefit costs	$ 2.9	$ 2.6	$ 2.9