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Investments - Gross Unrealized Gains and Losses and Cost of Equity (Detail) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | $ 36,020 | $ 36,020
Equity securities, Gross Unrealized Gains | 19,465 | 22,609
Equity securities, Gross Unrealized Losses | (9) |
Equity securities, Fair Value | 55,476 | 58,629
Domestic Common Stock [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | 36,020 | 36,020
Equity securities, Gross Unrealized Gains | 19,465 | 22,609
Equity securities, Gross Unrealized Losses | (9) |
Equity securities, Fair Value | $ 55,476 | $ 58,629

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