Employee Benefit Plans - Investments of the Plan Measured at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 1,879.6	$ 1,854.4	$ 1,800.5
Commingled trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	679.5	829.5
Commingled trusts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
Commingled trusts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	679.5	829.5
Commingled trusts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	490.4	351.7
U.S. government securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
U.S. government securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	490.4	351.7
U.S. government securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets		297.2
Mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets		18.2
Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets		279.0
Mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0.0
Corporate and municipal bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	695.4	355.1
Corporate and municipal bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
Corporate and municipal bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	695.4	355.1
Corporate and municipal bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
Mortgage-backed security bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	3.9	18.7
Mortgage-backed security bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
Mortgage-backed security bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	3.9	18.7
Mortgage-backed security bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	0.0
Total pension asset investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1,869.2	1,852.2
Total pension asset investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0.0	18.2
Total pension asset investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1,869.2	1,834.0
Total pension asset investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 0.0	$ 0.0