Leases - Additional Information (Details) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($) option_to_renew
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 26
Weighted average remaining lease term (in years)	7 years
Weighted average discount rate	2.31%
Operating leases, not yet commenced, lease obligations	$ 507
Minimum
Lessee, Lease, Description [Line Items]
Number of renewal options | option_to_renew	1
Operating leases, non-cancellable lease terms	5 years
Maximum
Lessee, Lease, Description [Line Items]
Operating leases, non-cancellable lease terms	15 years