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Fair Value Measurements (Tables) | 3 Months Ended
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Mar. 31, 2025
Fair Value Disclosures [Abstract] |
Assets And Liabilities Measured At Fair value, On A Recurring Basis | The following tables present the assets and liabilities measured at fair value on a recurring basis as of March 31, 2025 and December 31, 2024 by level:
(In thousands) | Total |  | Level 1 |  | Level 2 |  | Level 3
March 31, 2025 |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Fixed maturity securities available for sale: |  |  |  |  |  |  |
U.S. government and government agency | $ | 2,926,978 |  |  | $ | — |  |  | $ | 2,926,978 |  |  | $ | — |
State and municipal | 2,196,033 |  |  | — |  |  | 2,196,033 |  |  | — |
Mortgage-backed | 4,095,213 |  |  | — |  |  | 4,095,213 |  |  | — |
Asset-backed | 3,971,671 |  |  | — |  |  | 3,971,671 |  |  | — |
Corporate | 8,560,358 |  |  | — |  |  | 8,540,575 |  |  | 19,783 |
Foreign government | 1,825,632 |  |  | — |  |  | 1,825,632 |  |  | — |
Total fixed maturity securities available for sale | 23,575,885 |  |  | — |  |  | 23,556,102 |  |  | 19,783 |
Equity securities: |  |  |  |  |  |  |
Common stocks | 682,677 |  |  | 679,627 |  |  | 1,011 |  |  | 2,039 |
Preferred stocks | 462,363 |  |  | — |  |  | 457,529 |  |  | 4,834 |
Total equity securities | 1,145,040 |  |  | 679,627 |  |  | 458,540 |  |  | 6,873 |
Arbitrage trading account | 831,705 |  |  | 744,189 |  |  | 83,974 |  |  | 3,542 |
Total | $ | 25,552,630 |  |  | $ | 1,423,816 |  |  | $ | 24,098,616 |  |  | $ | 30,198 |
Liabilities: |  |  |  |  |  |  |
Trading account securities sold but not yet purchased | $ | 52,407 |  |  | $ | 52,407 |  |  | $ | — |  |  | $ | — |
December 31, 2024 |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Fixed maturity securities available for sale: |  |  |  |  |  |  |
U.S. government and government agency | $ | 2,235,341 |  |  | $ | — |  |  | $ | 2,235,341 |  |  | $ | — |
State and municipal | 2,294,644 |  |  | — |  |  | 2,294,644 |  |  | — |
Mortgage-backed | 3,765,490 |  |  | — |  |  | 3,765,490 |  |  | — |
Asset-backed | 3,885,012 |  |  | — |  |  | 3,885,012 |  |  | — |
Corporate | 8,417,641 |  |  | — |  |  | 8,397,974 |  |  | 19,667 |
Foreign government | 1,755,325 |  |  | — |  |  | 1,755,325 |  |  | — |
Total fixed maturity securities available for sale | 22,353,453 |  |  | — |  |  | 22,333,786 |  |  | 19,667 |
Equity securities: |  |  |  |  |  |  |
Common stocks | 760,167 |  |  | 757,115 |  |  | 1,011 |  |  | 2,041 |
Preferred stocks | 443,621 |  |  | — |  |  | 439,947 |  |  | 3,674 |
Total equity securities | 1,203,788 |  |  | 757,115 |  |  | 440,958 |  |  | 5,715 |
Arbitrage trading account | 1,122,599 |  |  | 1,062,459 |  |  | 56,630 |  |  | 3,510 |
Total | $ | 24,679,840 |  |  | $ | 1,819,574 |  |  | $ | 22,831,374 |  |  | $ | 28,892 |
Liabilities: |  |  |  |  |  |  |
Trading account securities sold but not yet purchased | $ | 73,358 |  |  | $ | 73,358 |  |  | $ | — |  |  | $ | — |
Summarize Changes In Level 3 Assets | The following tables summarize changes in Level 3 assets and liabilities for the three months ended March 31, 2025 and for the year ended December 31, 2024:
Gains (Losses) Included In:
(In thousands) | Beginning Balance |  | Earnings (Losses) |  | Other Comprehensive Income (Losses) |  | Impairments |  | Purchases |  | Sales |  | Paydowns / Maturities |  | Transfers In / (Out) |  | Ending Balance
Three Months Ended March 31, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate | $ | 19,667 |  |  | $ | — |  |  | $ | 116 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 19,783 |
Total | 19,667 |  |  | — |  |  | 116 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 19,783 |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stocks | $ | 2,041 |  |  | $ | (2) |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 2,039 |
Preferred stocks | 3,674 |  |  | — |  |  | — |  |  | — |  |  | 1,160 |  |  | — |  |  | — |  |  | — |  |  | 4,834 |
Total | 5,715 |  |  | (2) |  |  | — |  |  | — |  |  | 1,160 |  |  | — |  |  | — |  |  | — |  |  | 6,873 |
Arbitrage trading account | 3,510 |  |  | 32 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  |  |  | 3,542 |
Total | $ | 28,892 |  |  | $ | 30 |  |  | $ | 116 |  |  | $ | — |  |  | $ | 1,160 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 30,198 |
Year Ended December 31, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed maturities securities available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate | $ | — |  |  | $ | — |  |  | $ | (333) |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 20,000 |  |  | $ | 19,667 |
Total | — |  |  | — |  |  | (333) |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 20,000 |  |  | 19,667 |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common stocks | $ | 1,558 |  |  | $ | 611 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | (128) |  |  | $ | — |  |  | $ | — |  |  | $ | 2,041 |
Preferred stocks | 3,695 |  |  | 36 |  |  | — |  |  | — |  |  | — |  |  | (57) |  |  | — |  |  | — |  |  | 3,674 |
Total | 5,253 |  |  | 647 |  |  | — |  |  | — |  |  | — |  |  | (185) |  |  | — |  |  | — |  |  | 5,715 |
Arbitrage trading account | 3,772 |  |  | (261) |  |  | — |  |  | — |  |  | — |  |  | (38) |  |  | — |  |  | 37 |  |  | 3,510 |
Total | $ | 9,025 |  |  | $ | 386 |  |  | $ | (333) |  |  | $ | — |  |  | $ | — |  |  | $ | (223) |  |  | $ | — |  |  | $ | 20,037 |  |  | $ | 28,892 |

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