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Investments - Gross Unrealized Gains and Losses and Cost of Equity (Detail) - USD ($) $ in Thousands | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | $ 50,115 | $ 50,185
Equity securities, Gross Unrealized Gains | 13,242 | 11,873
Equity securities | 63,357 | 62,058
Domestic Common Stock [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | 50,115 | 50,185
Equity securities, Gross Unrealized Gains | 13,242 | 11,873
Equity securities | $ 63,357 | $ 62,058

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