Pension and Other Postretirement Benefits - Schedule of Components of Periodic Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2024
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 23	$ 23
Interest cost	55	57
Pension benefits | Direct Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	23	23	$ 27
Interest cost	55	57	61
Expected return on plan assets	(52)	(50)	(45)
Amortization of deferred losses (gains)	9	5	12
Net periodic benefit costs	35	35	55
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	0
Interest cost	2	2	2
Expected return on plan assets	0	0	0
Amortization of deferred losses (gains)	(3)	(4)	(4)
Net periodic benefit costs	$ (1)	$ (1)	$ (2)