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Investments - Additional Information (Detail) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 USD ($) Security | Dec. 31, 2021 USD ($)
Marketable Securities [Line Items] |  |
Individual fixed maturity held in unrealized loss position | Security | 185 |
Individual fixed maturity held in unrealized loss position longer than 12 months | Security | 48 |
Number of fixed maturity securities, allowance for credit loss | Security | 464 |
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 239,000 | $ 195,000
Available-for-sale, Allowance for Credit Losses | 0 | 0
Held-to-Maturity Securities [Member] |  |
Marketable Securities [Line Items] |  |
Investments on deposit with regulatory agencies | 24,000,000.0 |
Corporate Bonds [Member] |  |
Marketable Securities [Line Items] |  |
Short-term investments | 9,900,000 | 55,800,000
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 196,000 | 143,000
Number of majority securities | Security | 22 |
States and Political Subdivisions [Member] |  |
Marketable Securities [Line Items] |  |
Short-term investments | $ 1,200,000 | 1,600,000
Fixed maturity securities, held-to-maturity, allowance for credit losses | $ 40,000 | $ 48,000
Number of majority securities | Security | 439 |
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member] |  |
Marketable Securities [Line Items] |  |
Short-term investments | $ 3,000,000.0 |
Corporate Fixed Income Securities [Member] | Maximum [Member] |  |
Marketable Securities [Line Items] |  |
Investments maturity period using default rate | 20 years |

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