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Investments - Gross Unrealized Gains and Losses and Cost of Equity (Detail) - USD ($) $ in Thousands | Sep. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | $ 50,394 | $ 44,175
Equity securities, Gross Unrealized Gains | 6,981 | 19,965
Equity securities | 57,375 | 64,140
Domestic Common Stock [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | 50,394 | 44,175
Equity securities, Gross Unrealized Gains | 6,981 | 19,965
Equity securities | $ 57,375 | $ 64,140

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