Summary of Significant Accounting Policies - Long-Lived Assets (Details) - USD ($)
$ in Millions |
12 Months Ended |
|
Dec. 31, 2019 |
Dec. 31, 2018 |
| Property, Plant and Equipment [Line Items] |
|
|
| Less: accumulated depreciation and amortization |
$ (17,027)
|
$ (15,823)
|
| Total property and equipment, net |
31,310
|
28,335
|
| Flight equipment |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Property and equipment, gross |
$ 36,713
|
33,898
|
| Flight equipment | Minimum |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Estimated useful life |
20 years
|
|
| Flight equipment | Maximum |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Estimated useful life |
34 years
|
|
| Ground property and equipment |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Property and equipment, gross |
$ 5,721
|
4,667
|
| Ground property and equipment | Minimum |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Estimated useful life |
3 years
|
|
| Ground property and equipment | Maximum |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Estimated useful life |
40 years
|
|
| Information technology-related assets |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Property and equipment, gross |
$ 3,276
|
3,361
|
| Information technology-related assets | Minimum |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Estimated useful life |
3 years
|
|
| Information technology-related assets | Maximum |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Estimated useful life |
15 years
|
|
| Flight and ground equipment under capital lease |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Property and equipment, gross |
$ 1,608
|
1,055
|
| Less: accumulated depreciation and amortization |
(546)
|
(566)
|
| Advance payments for equipment |
|
|
| Property, Plant and Equipment [Line Items] |
|
|
| Property and equipment, gross |
$ 1,019
|
$ 1,177
|