Leases Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Leases [Abstract]
Right-of-use assets (Other assets)	$ 505	$ 0
Current lease liabilities (Accrued expenses)	155	0
Noncurrent lease liabilities (Other liabilities)	$ 361	$ 0
Operating leases, weighted-average remaining term	5 years 1 month 6 days
Operating leases, weighted-average discount rate	2.70%