Investments Investments - Gross Proceeds from AFS debt securities (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Investments, Debt and Equity Securities [Abstract] | |||
| Gross proceeds from sales | $ 76 | $ 54 | $ 0 |
| Gross proceeds from maturities | 83 | 47 | 14 |
| Total | $ 159 | $ 101 | $ 14 |