Fair Value Measurements And Disclosure (Notional Amount Of Our Outstanding Derivative Positions) (Details) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Derivative [Line Items] | ||
| Notional amounts of outstanding derivative positions | $ 40,835 | $ 46,947 |
| Interest rate swaps | ||
| Derivative [Line Items] | ||
| Notional amounts of outstanding derivative positions | 0 | 853 |
| Cross-currency swaps | ||
| Derivative [Line Items] | ||
| Notional amounts of outstanding derivative positions | 40,745 | 42,325 |
| Interest rate locks | ||
| Derivative [Line Items] | ||
| Notional amounts of outstanding derivative positions | 0 | 3,500 |
| Foreign exchange contracts | ||
| Derivative [Line Items] | ||
| Notional amounts of outstanding derivative positions | $ 90 | $ 269 |