Pension and Other Postretirement Benefits (Schedule of Components of Periodic Benefit Costs) (Details) - USD ($) $ in Millions		12 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	[1]	$ 0	$ 0	$ 53
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		35	19
Interest cost		39	30
Net periodic benefit costs		48	51	44
Total periodic benefit costs		48	51	97
Pension Benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		35	19	2
Interest cost		39	30	10
Expected return on plan assets		(55)	(30)	(5)
Amortization of deferred losses		28	11	3
Other		1	7	1
Net periodic benefit costs		48	37	11
Settlement loss		0	0	4
Pension Benefits | Shared Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit costs		0	14	33
Settlement loss		0	0	49
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		2	1
Interest cost		3	2
Net periodic benefit costs		6	7	7
Total periodic benefit costs		6	7	7
Postretirement Benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		2	1	0
Interest cost		3	2	0
Expected return on plan assets		0	0	0
Amortization of deferred losses		1	1	0
Other		0	(1)	0
Net periodic benefit costs		6	3	0
Settlement loss		0	0	0
Postretirement Benefits | Shared Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit costs		0	4	7
Settlement loss		$ 0	$ 0	$ 0

[1] The settlement loss was primarily related to the legacy plans (See Note 15—Pension and Other Postretirement Benefits).