Leases - Supplemental Balance Sheet Information, Leases (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Leases [Abstract]
Operating lease right-of-use assets	$ 1,389	$ 1,271
Operating lease liabilities - current	318	280
Operating lease liabilities - noncurrent	$ 1,086	$ 987
Weighted-average remaining lease term	7 years	7 years
Weighted-average discount rate	3.50%	2.10%
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 noncurrent liabilities	Other noncurrent liabilities