Pension and Other Postretirement Benefits - Schedule of Reconciliation of Benefit Obligations, Plan Assets and Funded Status of the Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2023
Pension Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 682.7	$ 848.2
Service cost	7.9	8.2	$ 8.1
Interest cost	38.7	43.7	46.2
Benefits paid	(59.3)	(68.8)
Actuarial loss (gain)	9.1	(2.3)
Plan settlements	0.0	(147.2)
Other	(0.5)	0.9
Projected benefit obligation at end of year	678.6	682.7	848.2
Change in plan assets:
Fair value of plan assets at beginning of year	471.8	654.8
Actual return	48.0	18.5
Benefits paid	(59.3)	(68.8)
Contributions	67.9	14.5
Plan settlements	0.0	(147.2)
Fair value of plan assets at end of year	528.4	471.8	654.8
Funded status of the plans	(150.2)	(210.9)
Amounts recognized in the consolidated balance sheets:
Accrued liabilities - current	(3.3)	(3.3)
Accrued pension and postretirement benefits - noncurrent	(146.9)	(207.6)
Amounts recognized in the consolidated balance sheets	(150.2)	(210.9)
Other Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	172.8	182.3
Service cost	1.4	1.5	1.8
Interest cost	9.9	10.2	10.0
Benefits paid	(13.6)	(12.3)
Actuarial loss (gain)	0.6	(8.9)
Plan settlements	0.0	0.0
Other	0.0	0.0
Projected benefit obligation at end of year	171.1	172.8	182.3
Change in plan assets:
Fair value of plan assets at beginning of year	136.3	120.4
Actual return	17.0	25.6
Benefits paid	(13.6)	(12.3)
Contributions	3.6	2.6
Plan settlements	0.0	0.0
Fair value of plan assets at end of year	143.3	136.3	$ 120.4
Funded status of the plans	(27.8)	(36.5)
Amounts recognized in the consolidated balance sheets:
Accrued liabilities - current	(15.3)	(15.4)
Accrued pension and postretirement benefits - noncurrent	(12.5)	(21.1)
Amounts recognized in the consolidated balance sheets	$ (27.8)	$ (36.5)