Pension and Other Postretirement Benefits - Schedule of Fair Values of Pension Plan by Assets Category (Details) - Pension Benefits - USD ($) $ in Millions	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 528.4	$ 471.8	$ 654.8
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	23.2	7.2
Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	504.3	464.1
Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.9	0.5
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	23.2	7.2
Level 1 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	23.2	7.2
Level 1 | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
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
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.9	0.5
Level 2 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
Level 2 | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.0	0.0
Level 2 | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.9	0.5
Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	504.3	464.1
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
Net Asset Value | Commingled trust funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	504.3	464.1
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