Leases - Narrative (Details) $ in Millions	12 Months Ended
	Sep. 30, 2023 USD ($) operating_lease	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Leases [Abstract]
Cash paid for operating leases, operating cash flows	$ 170	$ 163	$ 167
Operating lease right-of-use asset additions	$ 247	$ 94	$ 162
Operating leases, weighted-average remaining term	6 years 2 months 12 days	5 years 8 months 12 days
Operating leases, weighted-average discount rate	4.20%	3.00%
Lessee, operating lease, lease not yet commenced, number of contracts | operating_lease	1
Lessee, operating lease, lease not yet commenced, term of contract	15 years
Lessee, operating lease, lease not yet commenced, undiscounted future minimum payments	$ 80