Leases - Operating ROU Assets and Liabilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Leases [Abstract]
Operating lease ROU assets	$ 730	[1]
Operating lease liabilities	$ 781
Weighted-average remaining lease term	7 years 2 months
Weighted-average discount rate (percent)	3.10%

[1] Reported net of level lease adjustments and exit cost obligations.