Leases - Other Information (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Leases [Abstract] | ||
| Operating cash flows for operating leases | $ 1,166 | $ 1,271 |
| Operating cash flows for finance leases | 27 | 22 |
| Financing cash flows for finance leases | $ 192 | $ 108 |