Investments - Debt Securities At Fair Value (Detail) - USD ($) $ in Millions |
Sep. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Debt securities, at fair value | $ 17,045 | $ 16,981 |
| Corporate debt securities [Member] | ||
| Debt securities, at fair value | 10,725 | 10,991 |
| Securities backed by real estate [Member] | ||
| Debt securities, at fair value | 2,182 | 1,940 |
| Money Market Instruments [Member] | ||
| Debt securities, at fair value | 2,109 | 2,185 |
| Other [Member] | ||
| Debt securities, at fair value | $ 2,029 | $ 1,865 |