Pension and Other Postretirement Benefits - Schedule of Components of Periodic Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 27	$ 30
Interest cost	61	52
Pension benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	27	30	$ 38
Interest cost	61	52	30
Expected return on plan assets	(45)	(40)	(50)
Amortization of deferred losses	12	23	31
Other	0	0	3
Net periodic benefit costs	55	65	52
Postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1
Interest cost	2	2
Postretirement benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1
Interest cost	2	2	2
Expected return on plan assets	0	0	0
Amortization of deferred losses	(4)	(4)	1
Other	0	0	0
Net periodic benefit costs	$ (2)	$ (1)	$ 4