Pension and Other Postretirement Benefits (Plan Assets By Level Grantor Trust) (Details) - Grantor Trust - USD ($) $ in Millions		Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	$ 228	$ 220
Grantor Trust Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		213	205
Grantor Trust Partnership Interest
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	15	15
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	213	205
Level 1 | Grantor Trust Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		213	205
Level 1 | Grantor Trust Partnership Interest
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0	0
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	15	15
Fair Value Measured at Net Asset Value Per Share | Grantor Trust Balanced Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fair Value Measured at Net Asset Value Per Share | Grantor Trust Partnership Interest
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	$ 15	$ 15

[1] The fair value of the assets in the Grantor Trust as of June 30, 2019 and the 21CF Grantor Trust attributable to the Company as of June 30, 2018 was $249 million and $265 million, respectively. The remaining assets held by the Grantor Trust and 21CF Grantor Trust not presented in the table above are cash and cash equivalents.

[2] As a practical expedient, partnership interests held in the Grantor Trust and 21CF Grantor Trust are based on the fair value obtained from the general partner.