Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
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]
Employer contributions	$ 9.9	$ 8.7
Pension Benefits | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	6.5	5.5	$ 6.7
Expected contributions for next fiscal year	19.3
Pension Benefits | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	3.3	3.2	3.3
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	3.3	3.2
Effect of one percentage point increase in the assumed health care cost trend rate on service and interest cost components	0.1
Effect of one percentage point increase in the assumed health care cost trend rate on postretirement benefit obligation	2.5
Effect of one percentage point decrease in the assumed health care cost trend rate on service and interest cost components	0.1
Effect of one percentage point decrease in the assumed health care cost trend rate on postretirement benefit obligation	$ 2.2
Other Benefits | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	76.00%
Other Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Plan's current allocation policy	24.00%
Defined Contribution Retirement and Savings Plans
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined contribution retirement and savings plans	$ 25.3	$ 24.8	$ 22.6