Leases - Supplemental Balance Sheet Information Related to Leases (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Right-of-use assets recorded in Other Assets	$ 446	$ 418
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses	Accrued expenses
Current lease liabilities recorded in Payables, accrued expenses and other current liabilities	$ 126	$ 106
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Deferred Income Taxes and Other Liabilities	Deferred Income Taxes and Other Liabilities
Non-current lease liabilities recorded in Deferred Income Taxes and Other Liabilities	$ 344	$ 336