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Changes in Level 3 Investments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Fair Value Disclosures [Abstract] |  |  |  |
Beginning balance | $ 0 | $ 3,787 | $ 0 | $ 4,571
Included in accumulated other comprehensive income (loss) | $ 0 | $ 3 | $ 0 | $ 10
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] | Other Comprehensive Income (Loss), Net of Tax | Other Comprehensive Income (Loss), Net of Tax | Other Comprehensive Income (Loss), Net of Tax | Other Comprehensive Income (Loss), Net of Tax
Included in earnings attributable to realized gains / losses | $ 0 | $ 24 | $ 0 | $ (148)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Realized Investment Gains (Losses) | Realized Investment Gains (Losses) | Realized Investment Gains (Losses) | Realized Investment Gains (Losses)
Amortization of bond premium and discount, net | $ 0 | $ 1 | $ 0 | $ 5
Purchases | 0 | 182 | 0 | 295
Sales | 0 | (428) | 0 | (1,164)
Ending balance | 0 | 3,569 | 0 | 3,569
Gains (losses) included in earnings attributable to the change in unrealized gains (losses) related to assets still held at end of reporting period | $ 0 | $ 31 | $ 0 | $ (131)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax | OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax | OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax | OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax

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