Leases - Narrative (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Lessee, Lease, Description [Line Items] | |||
| Operating lease expense | $ 629 | $ 363 | |
| Operating lease not yet commenced | $ 5,040 | ||
| Finance lease not yet commenced | $ 317 | ||
| Minimum | |||
| Lessee, Lease, Description [Line Items] | |||
| Lease not yet commenced, term | 1 year | ||
| Maximum | |||
| Lessee, Lease, Description [Line Items] | |||
| Lease not yet commenced, term | 25 years | ||