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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, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Marketable Securities [Line Items] |  |  |
Proceeds from sales | $ 41,905 | $ 50,992 | $ 40,579
Gross realized investment gains | 6,729 | 3,715 | 1,754
Gross realized investment (losses) | (173) | (51) | (21)
Net realized investment gains (losses) | 6,556 | 3,664 | 1,733
Other, including gains (losses) on calls and redemptions | 23 | (224) | (38)
Net realized gains (losses) on investments | 6,579 | 3,440 | 1,695
Fixed Maturity Securities Available for Sale [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Proceeds from sales | 28,292 | 42,505 | 28,191
Gross realized investment gains | 181 | 365 | 1,751
Gross realized investment (losses) | (173) | (51) | (21)
Net realized investment gains (losses) | 8 | 314 | 1,730
Other, including gains (losses) on calls and redemptions |  | (200) | (6)
Net realized gains (losses) on investments | 8 | (114) | 1,724
Equity Securities [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Proceeds from sales | 12,688 | 8,487 |
Gross realized investment gains | 6,548 | 3,350 |
Net realized investment gains (losses) | 6,548 | 3,350 |
Net realized gains (losses) on investments | 6,548 | 3,350 |
Other [Member] |  |  |
Marketable Securities [Line Items] |  |  |
Proceeds from sales | 925 |  | 12,388
Gross realized investment gains |  |  | 3
Net realized investment gains (losses) |  |  | 3
Other, including gains (losses) on calls and redemptions | 23 | 24 | (32)
Net realized gains (losses) on investments | $ 23 | $ 24 | $ (29)

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