Settlement and Other Risk Management Narrative (Details) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Settlement and Other Risk Management [Abstract] | ||
| Travelers cheques outstanding, notional value | $ 370 | $ 367 |
| Travelers cheques covered by collateral arrangements | $ 294 | $ 290 |