Pension and Other Postretirement Benefits - Schedule of Plan Assets and Grantor Trust Assets By Level (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022
Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	$ 266	$ 276
Money market funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	26	20
Domestic fixed income funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	66	143
Balanced funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	53	112
Domestic government obligations | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	120
Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	1	1
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	891	853	$ 801
Pension benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	12	18
Pension benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	156	189
Pension benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	488	383
Pension benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	118	136
Pension benefits | Balanced funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	69	78
Pension benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	48	49
Level 1 | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	266	276
Level 1 | Money market funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	26	20
Level 1 | Domestic fixed income funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	66	143
Level 1 | Balanced funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	53	112
Level 1 | Domestic government obligations | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	120
Level 1 | Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	1	1
Level 1 | Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	843	804
Level 1 | Pension benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	12	18
Level 1 | Pension benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	156	189
Level 1 | Pension benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	488	383
Level 1 | Pension benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	118	136
Level 1 | Pension benefits | Balanced funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	69	78
Level 1 | Pension benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Money market funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Domestic fixed income funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Balanced funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Domestic government obligations | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0
Fair Value Measured at Net Asset Value Per Share | Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	48	49
Fair Value Measured at Net Asset Value Per Share | Pension benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Pension benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Pension benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Pension benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Pension benefits | Balanced funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Fair Value Measured at Net Asset Value Per Share | Pension benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	$ 48	$ 49