Pension and Other Postretirement Benefits - Schedule of Fair Values of Other Postretirement Benefit Plans by Asset Category (Details) - USD ($) $ in Millions	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 114.7	136.3	$ 112.8
Other Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	17.0	0.0
Other Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	21.6
Other Benefits | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	97.7	114.7
Other Benefits | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	97.7	114.7
Other Benefits | Commingled trust funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Other Benefits | Commingled trust funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Other Benefits | Commingled trust funds | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	97.7	114.7
Other Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	17.0	21.6
Other Benefits | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	17.0	0.0
Other Benefits | Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	21.6
Other Benefits | Short-term investments | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 0.0	$ 0.0