Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	$ 0.0	$ 51.9	$ 0.0
Plan's current allocation policy	95.00%
Percentage increase in funding level to shift assets from return seeking to liability hedging	5.00%
Return Seeking Asset
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	75.00%
Liability Matching Assets
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	25.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Change in discount rate	$ (8.3)
Change in plan experience	0.4	3.1
Mortality update		5.4
Settlement charge	0.0	51.9	0.0
Employer contributions	67.9	14.5
Pension Benefits | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	64.8	11.3	0.0
Expected contributions for next fiscal year	23.5
Pension Benefits | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	3.2	3.2	3.6
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Change in plan experience	2.2	4.9
Mortality update	(3.0)	2.1
Demographic update	0.6
Settlement charge	0.0	0.0	0.0
Employer contributions	$ 3.6	2.6
Other Benefits | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	100.00%
Defined Contribution Retirement and Savings Plans
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined contribution retirement and savings plans	$ 27.6	$ 26.5	$ 23.3