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Investments - Gross Unrealized Gains and Losses and Cost of Equity (Detail) - USD ($) $ in Thousands | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | $ 36,020 | $ 44,046
Equity securities, Gross Unrealized Gains | 21,692 | 13,101
Equity securities, Gross Unrealized Losses | 0 |
Equity securities | 57,712 | 57,147
Domestic Common Stock [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | 36,020 | 44,046
Equity securities, Gross Unrealized Gains | 21,692 | 13,101
Equity securities, Gross Unrealized Losses | 0 |
Equity securities | $ 57,712 | $ 57,147

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