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Components of Net Realized Investment Gains (Losses) (Detail) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2023 | Mar. 31, 2022
Schedule Of Available For Sale Securities [Line Items] |  |  |
Total net realized investment gains (losses) |  | $ (1,520) | $ (25,385)
Equity securities, Gross realized gains |  | 627 | 1,806
Equity securities, Gross realized losses |  | (1,541) | (3,151)
Equity securities, Total net realized investment gains (losses) |  | (914) | (1,345)
Not Designated as Hedging Instrument | Interest Rate Swap |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |
Gross realized gains |  | 0 | 6,088
Gross realized losses |  | 0 | (1,364)
Total net realized investment gains (losses) | [1] | 0 | 4,724
Fixed Income Securities |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |
Gross realized gains |  | 5 | 206
Gross realized losses |  | (611) | (28,970)
Total net realized investment gains (losses) |  | $ (606) | $ (28,764)
[1] | Includes periodic net interest settlements related to the derivatives of $1.4 million for the quarter ended March 31, 2022.

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