Pension and Other Postretirement Benefits - Schedule of Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 9.9	$ 9.2	$ 9.5
Interest cost	46.9	53.0	52.1
Expected return on plan assets	(62.2)	(64.9)	(65.9)
Amortization of net loss	15.5	10.4	13.5
Amortization of prior service cost (benefit)	2.1	2.1	2.1
Net periodic benefit costs	12.2	9.8	11.3
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2.6	2.3	2.6
Interest cost	9.0	10.1	9.5
Expected return on plan assets	(7.1)	(7.0)	(6.9)
Amortization of net loss	2.5	1.6	2.9
Amortization of prior service cost (benefit)	(3.9)	(5.2)	(5.2)
Net periodic benefit costs	$ 3.1	$ 1.8	$ 2.9