Leases (Future Minimum Maturities of Lease Liabilities) (Details) $ in Millions	Sep. 30, 2019 USD ($)
Operating Leases [Abstract]
Remainder of 2019	$ 1,168
2020	4,643
2021	4,258
2022	3,993
2023	3,609
2024	2,923
Thereafter	11,706
Total lease payments	32,300
Less imputed interest	(6,559)
Total	25,741
Finance Leases [Abstract]
Remainder of 2019	100
2020	306
2021	287
2022	276
2023	264
2024	247
Thereafter	1,591
Total lease payments	3,071
Less inputed interest	(1,095)
Total	$ 1,976