Leases (Maturity of Lease Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Operating leases
2021	$ 205
2022	176
2023	144
2024	112
2025	76
Thereafter	113
Total lease payments	826
Less amount representing interest	(99)
Present value of lease liabilities	727
Finance leases
2021	63
2022	40
2023	28
2024	10
2025	1
Thereafter	3
Total lease payments	145
Less amount representing interest	(10)
Present value of lease liabilities	$ 135	$ 127