Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	$ (11.4)	$ 0.0	$ 0.0
Percentage increase in funding level to shift assets from return seeking to liability hedging	5.00%
Percentage change in assets allocation from assets seeking to liability hedging due to increase in funding level	4.00%
Return Seeking Asset
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	60.00%
Liability Matching Assets
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	40.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Mortality update	$ 13.1	15.2
Change in discount rate	7.1	(91.6)
Settlement charge	(11.4)	0.0	0.0
Employer contributions	23.7	9.9
Pension Benefits | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	19.9	6.5	5.5
Expected contributions for next fiscal year	0.0
Pension Benefits | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	3.8	3.3	3.2
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Mortality update	6.8	2.1
Change in discount rate		(16.6)
Change in plan experience	4.2
Settlement charge	0.0	0.0	0.0
Employer contributions	$ 2.7	3.3
Other Benefits | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	84.00%
Other Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	16.00%
Defined Contribution Retirement and Savings Plans
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined contribution retirement and savings plans	$ 19.2	$ 25.3	$ 24.8