Pension and Other Postretirement Benefits (Plan Assets By Level) (Details) - Pension Benefits - USD ($) $ in Millions		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 800	$ 70	$ 70
Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	83
Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	72
International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	132
International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	39
Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	198
U.S. common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	131
Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	17
Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	12
Corporate obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	44
Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		13
Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	32
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		27
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		500
Level 1 | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0
Level 1 | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	72
Level 1 | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	132
Level 1 | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0
Level 1 | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	136
Level 1 | U.S. common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	131
Level 1 | Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0
Level 1 | Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0
Level 1 | Corporate obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0
Level 1 | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 1 | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	32
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		(3)
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		186
Level 2 | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	83
Level 2 | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0
Level 2 | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0
Level 2 | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0
Level 2 | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0
Level 2 | U.S. common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0
Level 2 | Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	17
Level 2 | Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	12
Level 2 | Corporate obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	44
Level 2 | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 2 | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		30
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[4]	114
Fair Value Measured at Net Asset Value Per Share | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1],[4]	0
Fair Value Measured at Net Asset Value Per Share | Domestic equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1],[4]	0
Fair Value Measured at Net Asset Value Per Share | International equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1],[4]	0
Fair Value Measured at Net Asset Value Per Share | International fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1],[4]	39
Fair Value Measured at Net Asset Value Per Share | Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1],[4]	62
Fair Value Measured at Net Asset Value Per Share | U.S. common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2],[4]	0
Fair Value Measured at Net Asset Value Per Share | Domestic government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3],[4]	0
Fair Value Measured at Net Asset Value Per Share | Domestic agency obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3],[4]	0
Fair Value Measured at Net Asset Value Per Share | Corporate obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3],[4]	0
Fair Value Measured at Net Asset Value Per Share | Partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[4]	13
Fair Value Measured at Net Asset Value Per Share | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2],[4]	0
Fair Value Measured at Net Asset Value Per Share | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[4]	$ 0

[1] Open-ended pooled funds that are registered and/or available to the general public are valued at the daily published NAV.

[2] Common stock investments that are publicly traded and exchange traded funds 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] As a practical expedient, pooled funds are valued at the net asset value (“NAV”) provided by the fund issuer and partnership interests are based on the fair value obtained from the general partner.