Pension and Other Postretirement Benefits - Schedule of Components of Periodic Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2021
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 30	$ 38
Interest cost	52	30
Pension benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	30	38	$ 38
Interest cost	52	30	30
Expected return on plan assets	(40)	(50)	(50)
Amortization of deferred losses	23	31	44
Other	0	3	2
Net periodic benefit costs	65	52	64
Postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	2	2
Postretirement benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2
Interest cost	2	2	2
Expected return on plan assets	0	0	0
Amortization of deferred losses	(4)	1	1
Other	0	0	0
Net periodic benefit costs	$ (1)	$ 4	$ 5