Pension and Other Postretirement Benefits - Schedule of Fair Values of Pension Plan by Assets Category (Details) - USD ($) $ in Millions	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 999.4	923.4	$ 964.7
Pension Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	21.6	6.6
Pension Benefits | Domestic and international equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	156.3	125.9
Pension Benefits | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	404.9	378.8
Pension Benefits | Limited partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	52.4	45.6
Pension Benefits | Government agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	176.2	187.4
Pension Benefits | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	183.1	176.1
Pension Benefits | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	2.4	1.6
Pension Benefits | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	2.5	1.4
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	166.3	135.0
Pension Benefits | Level 1 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 1 | Domestic and international equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	156.3	125.9
Pension Benefits | Level 1 | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 1 | Limited partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 1 | Government agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	7.5
Pension Benefits | Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	7.6	0.0
Pension Benefits | Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	2.4	1.6
Pension Benefits | Level 1 | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	375.8	364.0
Pension Benefits | Level 2 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	21.6	6.6
Pension Benefits | Level 2 | Domestic and international equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 2 | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 2 | Limited partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 2 | Government agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	176.2	179.9
Pension Benefits | Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	175.5	176.1
Pension Benefits | Level 2 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Level 2 | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	2.5	1.4
Pension Benefits | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	457.3	424.4
Pension Benefits | Net Asset Value | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Net Asset Value | Domestic and international equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Net Asset Value | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	404.9	378.8
Pension Benefits | Net Asset Value | Limited partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	52.4	45.6
Pension Benefits | Net Asset Value | Government agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Net Asset Value | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Net Asset Value | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Pension Benefits | Net Asset Value | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 0.0	$ 0.0