Pension and Other Postretirement Benefits - Schedule of Fair Values of Pension Plan by Assets Category (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 471.8	654.8	$ 759.4
Pension Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	7.2	6.7
Pension Benefits | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	464.1	646.8
Pension Benefits | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.5	1.3
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	7.2	6.7
Pension Benefits | Level 1 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	7.2	6.7
Pension Benefits | Level 1 | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
Pension Benefits | Level 1 | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.5	1.3
Pension Benefits | Level 2 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
Pension Benefits | Level 2 | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
Pension Benefits | Level 2 | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.5	1.3
Pension Benefits | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	464.1	646.8
Pension Benefits | Net Asset Value | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
Pension Benefits | Net Asset Value | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	464.1	646.8
Pension Benefits | Net Asset Value | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 0.0	$ 0.0