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Investments - Additional Information (Detail) $ in Thousands | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2022 USD ($) Security | Sep. 30, 2021 USD ($) | Sep. 30, 2022 USD ($) Security | Sep. 30, 2021 USD ($) | Jun. 30, 2022 USD ($) | Dec. 31, 2021 USD ($)
Marketable Securities [Line Items] |  |  |  |  |  |
Individual fixed maturity held in unrealized loss position | Security | 222 |  | 222 |  |  |
Number of fixed maturity securities, allowance for credit loss | Security | 484 |  | 484 |  |  |
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 255 |  | $ 255 |  | $ 276 | $ 195
Available-for-sale, Allowance for Credit Losses | 0 |  | 0 |  |  | 0
Net realized gains (losses) on investments | 585 | $ (8) | 2,402 | $ 1,490 |  |
Net unrealized gains (losses) on equity securities | (4,082) | $ (771) | (12,984) | $ 8,026 |  |
Corporate Bonds [Member] |  |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |  |
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 208 |  | $ 208 |  | 228 | 143
Number of majority securities | Security | 23 |  | 23 |  |  |
States and Political Subdivisions [Member] |  |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |  |
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 44 |  | $ 44 |  | $ 44 | $ 48
Number of majority securities | Security | 458 |  | 458 |  |  |
Corporate Fixed Income Securities [Member] | Maximum [Member] |  |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |  |
Investments maturity period using default rate |  |  | 20 years |  |  |

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