Pension and Other Postretirement Benefits - Plan Assets and Grantor Trust Assets By Level (Details) - USD ($) $ in Millions	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	$ 270	$ 304
Grantor Trust Balanced Funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	234	267
Grantor Trust Partnership Interest | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	16	17
Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	20	20
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	801	972	$ 788
Pension benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	20	22
Pension benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	82	67
Pension benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	381	355
Pension benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	133	193
Pension benefits | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		28
Pension benefits | Balanced funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	78	93
Pension benefits | U.S. Common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	43	136
Pension benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	33	10
Pension benefits | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	32	67
Pension benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	(1)	1
Level 1 | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	254	287
Level 1 | Grantor Trust Balanced Funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	234	267
Level 1 | Grantor Trust Partnership Interest | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 1 | Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	20	20
Level 1 | Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	768	961
Level 1 | Pension benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	20	22
Level 1 | Pension benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	82	67
Level 1 | Pension benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	381	355
Level 1 | Pension benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	133	193
Level 1 | Pension benefits | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		28
Level 1 | Pension benefits | Balanced funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	78	93
Level 1 | Pension benefits | U.S. Common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	43	136
Level 1 | Pension benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 1 | Pension benefits | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	32	67
Level 1 | Pension benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	(1)	0
Level 2 | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Grantor Trust Balanced Funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Grantor Trust Partnership Interest | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	1
Level 2 | Pension benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		0
Level 2 | Pension benefits | Balanced funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | U.S. Common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	0
Level 2 | Pension benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	0	1
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	16	17
Fair Value Measured at Net Asset Value Per Share | Grantor Trust 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 | Grantor Trust Partnership Interest | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	16	17
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	33	10
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 | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		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 | U.S. Common stocks
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	33	10
Fair Value Measured at Net Asset Value Per Share | Pension benefits | Exchange traded 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 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	$ 0	$ 0