Leases Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Operating leases, weighted-average remaining term	4 years 7 months 6 days
Operating leases, weighted-average discount rate	2.80%
Other Assets [Member]
Operating lease right-of-use assets	$ 508	$ 0
Other Current Liabilities [Member]
Current lease liabilities (Accrued expenses)	148	0
Other Liabilities [Member]
Noncurrent lease liabilities (Other liabilities)	$ 373	$ 0