Leases (Maturity of Lease Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Operating leases
2020	$ 157
2021	186
2022	149
2023	115
2024	81
Thereafter	103
Total lease payments	791
Less amount representing interest	(84)
Present value of lease liabilities	707
Finance leases
2020	45
2021	55
2022	31
2023	18
2024	2
Thereafter	6
Total lease payments	157
Less amount representing interest	(11)
Present value of lease liabilities	$ 146	$ 127