Leases - Lease Assets and Liabilities Included in the Consolidated Statement of Financial Position (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Leases [Abstract]
Operating lease right-of-use assets	$ 259	$ 248
Operating lease liabilities - current	82	78
Operating lease liabilities - noncurrent	176	168
Present value of lease liabilities	$ 258	$ 246
Operating lease right of use asset, statement of financial position, extensible list	Other noncurrent liabilities	Other noncurrent liabilities
Operating lease liability, current, statement of financial position, extensible list	Other current liabilities	Other current liabilities
Operating lease liability, noncurrent, statement of financial position, extensible list	Other noncurrent liabilities	Other noncurrent liabilities
Weighted average remaining lease term:
Operating leases	5 years	5 years
Weighted average discount rate:
Operating leases	6.00%	6.20%