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v3.23.3

Investments (Narrative) (Detail) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2023 USD ($) Security | Sep. 30, 2022 USD ($) | Sep. 30, 2023 USD ($) Security | Sep. 30, 2022 USD ($) | Dec. 31, 2022 USD ($) Security
Schedule Of Investments [Line Items] |  |  |  |  |
Fair value of securities on deposit with various regulatory authorities | $ 10 |  | $ 10 |  | $ 10
Number of securities in unrealized loss position for a continuous 12 month period | Security | 589 |  | 589 |  | 210
Rate that a security's fair value is below book value | 5.00% |  | 5.00% |  | 5.00%
Increase decrease in other net realized (gains) losses |  |  | $ 30 | $ 13 |
Asset Pledged as Collateral [Member] |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |
Fair value of securities pledged as collateral | $ 209 |  | $ 209 |  | $ 251
Securities In Unrealized Loss Position [Member] |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |
Weighted average contractual maturity period in years for securities in an unrealized loss position |  |  | 13 years |  | 14 years
Increase decrease in other net realized (gains) losses | $ 8 | $ 2 | $ 8 | $ 21 |
Fair Value Below Book Value Greater Than Five Percent [Member] |  |  |  |  |
Schedule Of Investments [Line Items] |  |  |  |  |
Number of securities in unrealized loss position for a continuous 12 month period | Security | 509 |  | 509 |  | 190

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