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Investments - Gross Unrealized Gains and Losses and Cost of Equity (Detail) - USD ($) $ in Thousands | Jun. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | $ 49,422 | $ 44,175
Equity securities, Gross Unrealized Gains | 11,063 | 19,965
Equity securities, Fair Value | 60,485 | 64,140
Domestic Common Stock [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities, Cost | 49,422 | 44,175
Equity securities, Gross Unrealized Gains | 11,063 | 19,965
Equity securities, Fair Value | $ 60,485 | $ 64,140

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