Leases - Schedule of Operating Lease Right of Use Assets and Operating Lease Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2025	Sep. 30, 2024
Leases [Abstract]
Operating lease right-of-use assets	$ 254	$ 248
Operating lease liabilities - current	84	78
Operating lease liabilities - noncurrent	169	168
Present value of lease liabilities	$ 253	$ 246
Weighted average remaining lease term:
Operating leases	5 years	5 years
Weighted average discount rate:
Operating leases	6.20%	6.20%
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other noncurrent assets	Other noncurrent assets
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Noncurrent	Other Liabilities, Noncurrent