Leases - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Lessee, Lease, Description [Line Items]
Operating lease, weighted average remaining lease term (in years)	8 years 3 months 18 days
Operating lease, weighted average discount rate, percent	4.60%
Operating lease, cost	$ 196	$ 190	$ 145
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (in years)	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract (in years)	25 years