Pension and Other Postretirement Benefits (Schedule of Components of Periodic Benefit Costs) (Details) - USD ($) $ in Millions		12 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	[1]	$ 0	$ 53	$ 25
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		19	2
Interest cost		30	10
Net periodic benefit costs		51	44	50
Total periodic benefit costs		51	97	75
Pension Benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		19	2	2
Interest cost		30	10	9
Expected return on plan assets		(30)	(5)	(4)
Amortization of deferred losses		11	3	3
Other		7	1	1
Net periodic benefit costs		37	11	11
Settlement loss		0	4	4
Pension Benefits | Shared Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit costs		14	33	39
Settlement loss		0	49	21
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		1	0
Interest cost		2	0
Net periodic benefit costs		7	7	9
Total periodic benefit costs		7	7	9
Postretirement Benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		1	0	0
Interest cost		2	0	0
Expected return on plan assets		0	0	0
Amortization of deferred losses		1	0	0
Other		(1)	0	0
Net periodic benefit costs		3	0	0
Settlement loss		0	0	0
Postretirement Benefits | Shared Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit costs		4	7	9
Settlement loss		$ 0	$ 0	$ 0

[1] The settlement loss was primarily related to the Shared Plans (See Note 14—Pension and Other Postretirement Benefits).