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Investments - A Summary of the Company's Realized Gains and Losses on Sales, Calls or Redemptions of Investments (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Marketable Securities [Line Items] |  |  |
Proceeds from sales | $ 34,260 | $ 41,905 | $ 50,992
Gross realized investment gains | 1,054 | 6,729 | 3,715
Gross realized investment (losses) | (1,446) | (173) | (51)
Net realized investment gains (losses) | (392) | 6,556 | 3,664
Other, including gains (losses) on calls and redemptions | (184) | 23 | (224)
Net realized gains (losses) on investments | (576) | 6,579 | 3,440
Fixed Maturity Securities Available for Sale [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Proceeds from sales | 26,327 | 28,292 | 42,505
Gross realized investment gains | 10 | 181 | 365
Gross realized investment (losses) | (310) | (173) | (51)
Net realized investment gains (losses) | (300) | 8 | 314
Other, including gains (losses) on calls and redemptions | 129 |  | (200)
Net realized gains (losses) on investments | (171) | 8 | 114
Equity Securities [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Proceeds from sales | 7,933 | 12,688 | 8,487
Gross realized investment gains | 1,044 | 6,548 | 3,350
Gross realized investment (losses) | (1,136) |  |
Net realized investment gains (losses) | (92) | 6,548 | 3,350
Net realized gains (losses) on investments | (92) | 6,548 | 3,350
Other [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Proceeds from sales |  | 925 |
Other, including gains (losses) on calls and redemptions | (313) | 23 | (24)
Net realized gains (losses) on investments | $ (313) | $ 23 | $ (24)

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