Pension and Other Postretirement Benefits - Schedule of Fair Values of Pension Plan by Assets Category (Details) - Pension Benefits - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 987.6	$ 885.1	$ 985.8
Net Asset Value	420.7	378.6
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	24.0	15.3
Domestic and international equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	148.3	139.4
Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value	376.6	338.2
Limited partnerships
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value	42.3	38.5
Government agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	154.4	141.7
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	236.2	197.3
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value	1.8	1.9
Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	4.0	12.8
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	161.1	140.1
Level 1 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	9.4	0.0
Level 1 | Domestic and international equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	148.3	139.4
Level 1 | Government agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	3.4	0.7
Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Level 1 | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	405.8	366.4
Level 2 | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	14.6	15.3
Level 2 | Domestic and international equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	0.0	0.0
Level 2 | Government agency bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	151.0	141.0
Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	236.2	197.3
Level 2 | Mortgage/asset backed securities and other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 4.0	$ 12.8