Leases - Supplemental Cash Flow Information, Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Cash paid for amounts included in the measurement of lease liability:
Operating cash outflows from operating leases	$ 373	$ 367	$ 398
Noncash operating lease activity:
Right-of-use assets obtained in exchange for operating lease liabilities	$ 427	$ 369	$ 515