Pension and Other Postretirement Benefits - Schedule of Components of Net Periodic Benefit Cost (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
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	7.9	8.2	8.1
Interest cost	38.7	43.7	46.2
Expected return on plan assets	(29.7)	(35.9)	(45.3)
Amortization of net loss (gain)	7.3	8.0	9.5
Amortization of prior service cost (benefit)	2.1	2.1	2.1
Settlement charge	0.0	51.9	0.0
Net pension expense (income)	26.3	78.0	20.6
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.4	1.5	1.8
Interest cost	9.9	10.2	10.0
Expected return on plan assets	(8.4)	(7.3)	(6.8)
Amortization of net loss (gain)	(5.6)	(2.5)	(1.8)
Amortization of prior service cost (benefit)	1.2	(3.9)	(3.9)
Settlement charge	0.0	0.0	0.0
Net pension expense (income)	$ (1.5)	$ (2.0)	$ (0.7)