Fair Value Measurements - Recurring Reconciliation (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Reconciliation of items measured at fair value on a recurring basis that used significant unobservable inputs (Level 3) | |||
| Balance at the beginning of the period | $ 46 | $ 40 | $ 30 |
| Total gains or losses included in earnings | 0 | 0 | 0 |
| Total gains or losses included in other comprehensive income | 0 | 0 | 0 |
| Purchases and issuances | 10 | 9 | 13 |
| Sales and settlements | (22) | (3) | (3) |
| Transfers in and/or out of Level 3 | 0 | 0 | 0 |
| Balance at the end of the period | 34 | 46 | 40 |
| Total gains or losses included in other comprehensive income | $ 0 | $ 0 | $ 0 |