Pension and Other Postretirement Benefits (Plan Assets and Grantor Trust Assets By Level) (Details) - USD ($) $ in Millions		Jun. 30, 2021	Jun. 30, 2020		Jun. 30, 2019
Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		$ 304	$ 247
Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		20	20
Grantor Trust Balanced Funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	267	214
Grantor Trust Partnership Interest | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		17	13
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		972	788		$ 800
Pension Benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	22	33
Pension Benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	67	73
Pension Benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		355	3
Pension Benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	193	119
Pension Benefits | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		28	29
Pension Benefits | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	93	181
Pension Benefits | U.S. Common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		136	144	[2]
Pension Benefits | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		67	70
Pension Benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		1	30
Pension Benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		10	13
Pension Benefits | Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3]		19
Pension Benefits | Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3]		24
Pension Benefits | Corporate Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset			50
Level 1 | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		287	234
Level 1 | Other | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		20	20
Level 1 | Grantor Trust Balanced Funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	267	214
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 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		961	514
Level 1 | Pension Benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	22	0
Level 1 | Pension Benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	67	73
Level 1 | Pension Benefits | Domestic fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		355	3
Level 1 | Pension Benefits | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	193	119
Level 1 | Pension Benefits | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		28	1
Level 1 | Pension Benefits | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	93	114
Level 1 | Pension Benefits | U.S. Common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		136	144	[2]
Level 1 | Pension Benefits | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		67	70
Level 1 | Pension Benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		0	(10)
Level 1 | Pension Benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		0	0
Level 1 | Pension Benefits | Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3]		0
Level 1 | Pension Benefits | Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3]		0
Level 1 | Pension Benefits | Corporate Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset			0
Level 2 | 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 | Grantor Trust Balanced Funds | Trust for Benefit of Employees
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	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 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		1	166
Level 2 | Pension Benefits | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	0	33
Level 2 | Pension Benefits | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	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	[1]	0	0
Level 2 | Pension Benefits | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		0	0
Level 2 | Pension Benefits | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1]	0	0
Level 2 | Pension Benefits | U.S. Common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		0	0	[2]
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		1	40
Level 2 | Pension Benefits | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset		0	0
Level 2 | Pension Benefits | Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3]		19
Level 2 | Pension Benefits | Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3]		24
Level 2 | Pension Benefits | Corporate Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset			50
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	[4]	17	13
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	[4]	0	0
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	[1],[4]	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	[4]	17	13
Fair Value Measured at Net Asset Value Per Share | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[4]	10	108
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	[1],[4]	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	[1],[4]	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	[4]	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	[1],[4]	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	[4]	0	28
Fair Value Measured at Net Asset Value Per Share | Pension Benefits | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[1],[4]	0	67
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	[4]	0	0	[2]
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	[4]	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	[4]	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	[4]	$ 10	13
Fair Value Measured at Net Asset Value Per Share | Pension Benefits | Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3],[4]		0
Fair Value Measured at Net Asset Value Per Share | Pension Benefits | Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[3],[4]		0
Fair Value Measured at Net Asset Value Per Share | Pension Benefits | Corporate Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan asset	[4]		$ 0

[1] Pooled funds that have a readily determinable fair value are valued at the regularly published NAV.

[2] Exchange traded funds and common stock investments that are publicly traded are valued at the closing price reported on active markets in which the securities are traded.

[3] The fair value of corporate, government and agency obligations are valued based on a compilation of primary observable market information or a broker quote in a non-active market.

[4] Investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are excluded from the fair value hierarchy disclosure. These investments have monthly liquidity.