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Investments - Additional Information (Detail) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 USD ($) Security | Dec. 31, 2022 USD ($)
Marketable Securities [Line Items] |  |
Short-term investments | $ 0 |
Individual fixed maturity held in unrealized loss position | Security | 156 |
Individual fixed maturity held in unrealized loss position longer than 12 months | Security | 134 |
Number of fixed maturity securities, allowance for credit loss | Security | 471 |
Fixed maturity securities, available-for-sale, allowance for credit losses | $ 0 | $ 0
Fixed maturity securities, held-to-maturity, allowance for credit losses | 182,000 | 239,000
Held-to-Maturity Securities [Member] |  |
Marketable Securities [Line Items] |  |
Investments on deposit with regulatory agencies | 24,400,000 |
Corporate Bonds [Member] |  |
Marketable Securities [Line Items] |  |
Short-term investments |  | 9,900,000
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 142,000 | 196,000
Number of majority securities | Security | 451 |
States and Political Subdivisions [Member] |  |
Marketable Securities [Line Items] |  |
Short-term investments |  | 1,200,000
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 38,000 | 40,000
Number of majority securities | Security | 17 |
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member] |  |
Marketable Securities [Line Items] |  |
Short-term investments |  | $ 3,000,000
Corporate Fixed Income Securities [Member] | Maximum [Member] |  |
Marketable Securities [Line Items] |  |
Investments maturity period using default rate | 20 years |

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