Leases Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Right-of-use assets (Other assets)	$ 500	$ 0
Current lease liabilities (Accrued expenses)	149	0
Noncurrent lease liabilities (Other liabilities)	$ 359	$ 0
Operating leases, weighted-average remaining term	5 years 2 months 12 days
Operating leases, weighted-average discount rate	3.00%