Revenue Recognition - Trade Allowance for Credit Losses (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
|
| Roll forward of notes and accounts receivable - trade allowance for credit losses | ||
| Allowance for Credit Loss, Beginning Balance | $ 299 | $ 309 |
| Additions / (Releases) | 76 | 98 |
| Write-offs | (46) | (113) |
| Other | 5 | 5 |
| Allowance for Credit Loss, Ending Balance | 351 | 299 |
| Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment | ||
| Roll forward of notes and accounts receivable - trade allowance for credit losses | ||
| Allowance for Credit Loss, Beginning Balance | $ 316 | |
| Allowance for Credit Loss, Ending Balance | $ 316 | |