Investments - Equity Securities At Fair Value (Detail) - USD ($) $ in Millions |
Sep. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Equity securities, at fair value | $ 19,339 | $ 19,781 |
| Public Equity [Member] | ||
| Percentage of investment in equity securities | 21.00% | 15.00% |
| Private Equity [Member] | ||
| Percentage of investment in equity securities | 79.00% | 85.00% |
| Public And Private Equity [Member] | ||
| Percentage of investment in equity securities | 100.00% | 100.00% |
| Corporate [Member] | ||
| Percentage of investment in equity securities | 80.00% | 83.00% |
| Real Estate [Member] | ||
| Percentage of investment in equity securities | 20.00% | 17.00% |
| Corporate And Real Estate [Member] | ||
| Percentage of investment in equity securities | 100.00% | 100.00% |