Investments (Tables)
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9 Months Ended |
Sep. 30, 2026 |
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| Investments, Debt and Equity Securities [Abstract] |
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| Schedule of Disposition of Fixed Income and Equity Securities |
| | | | | | | | | | | | | Sales | | Proceeds | | Gross Realized | | Net Realized | (in thousands) | | From Sales | | Gains | | Losses | | Gain (Loss) | 2026 | | | | | | | | | | | | | Fixed income securities - available-for-sale | | $ | 172,041 | | $ | 1,483 | | $ | (3,393) | | $ | (1,910) | Equity securities | | | 57,760 | | | 32,234 | | | (2,169) | | | 30,065 | 2025 | | | | | | | | | | | | | Fixed income securities - available-for-sale | | $ | 383,956 | | $ | 5,076 | | $ | (3,219) | | $ | 1,857 | Equity securities | | | 87,874 | | | 46,478 | | | (991) | | | 45,487 | | | | | | | | | | | | | | Calls/Maturities | | | | | Gross Realized | | Net Realized | (in thousands) | | Proceeds | | Gains | | Losses | | Gain (Loss) | 2026 | | | | | | | | | | | | | Fixed income securities - available-for-sale | | $ | 353,357 | | $ | 673 | | $ | (600) | | $ | 73 | 2025 | | | | | | | | | | | | | Fixed income securities - available-for-sale | | $ | 344,629 | | $ | 271 | | $ | (72) | | $ | 199 |
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| Fair Value, Assets Measured on Recurring Basis |
| | | | | | | | | | | | | | | As of September 30, 2026 | | | Quoted Prices in | | Significant Other | | Significant | | | | | | Active Markets for | | Observable | | Unobservable | | | | | | Identical Assets | | Inputs | | Inputs | | | | (in thousands) | | (Level 1) | | (Level 2) | | (Level 3) | | Total | Fixed income securities - available-for-sale | | | | | | | | | | | | | U.S. government | | $ | — | | $ | 245,973 | | $ | — | | $ | 245,973 | U.S. agency | | | — | | | 24,887 | | | — | | | 24,887 | Non-U.S. government & agency | | | — | | | 13,603 | | | 2,028 | | | 15,631 | Agency MBS | | | — | | | 580,245 | | | — | | | 580,245 | ABS/CMBS/MBS* | | | — | | | 781,895 | | | — | | | 781,895 | Corporate | | | — | | | 1,487,800 | | | 136,154 | | | 1,623,954 | Municipal | | | — | | | 328,384 | | | — | | | 328,384 | Total fixed income securities - available-for-sale | | $ | — | | $ | 3,462,787 | | $ | 138,182 | | $ | 3,600,969 | Equity securities | | | 937,282 | | | — | | | 11,037 | | | 948,319 | Total | | $ | 937,282 | | $ | 3,462,787 | | $ | 149,219 | | $ | 4,549,288 |
| | | | | | | | | | | | | | | As of December 31, 2025 | | | Quoted Prices in | | Significant Other | | Significant | | | | | | Active Markets for | | Observable | | Unobservable | | | | | | Identical Assets | | Inputs | | Inputs | | | | (in thousands) | | (Level 1) | | (Level 2) | | (Level 3) | | Total | Fixed income securities - available-for-sale | | | | | | | | | | | | | U.S. government | | $ | — | | $ | 335,223 | | $ | — | | $ | 335,223 | U.S. agency | | | — | | | 37,927 | | | — | | | 37,927 | Non-U.S. government & agency | | | — | | | 11,417 | | | 2,130 | | | 13,547 | Agency MBS | | | — | | | 610,675 | | | — | | | 610,675 | ABS/CMBS/MBS* | | | — | | | 672,984 | | | — | | | 672,984 | Corporate | | | — | | | 1,383,329 | | | 108,177 | | | 1,491,506 | Municipal | | | — | | | 371,474 | | | — | | | 371,474 | Total fixed income securities - available-for-sale | | $ | — | | $ | 3,423,029 | | $ | 110,307 | | $ | 3,533,336 | Equity securities | | | 890,622 | | | — | | | 8,254 | | | 898,876 | Total | | $ | 890,622 | | $ | 3,423,029 | | $ | 118,561 | | $ | 4,432,212 |
* | Non-agency asset-backed, commercial mortgage-backed and mortgage-backed securities |
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| Summary of Changes in Balance of Level 3 Securities |
| | | | | | | | | | | | | | | Three Months Ended September 30, | | Nine Months Ended September 30, | (in thousands) | | 2026 | | 2025 | | 2026 | | 2025 | Beginning balance | | $ | 144,584 | | $ | 101,534 | | $ | 118,561 | | $ | 95,125 | Net realized and unrealized gains (losses) | | | | | | | | | | | | | Included in other comprehensive earnings (loss) | | | (3,826) | | | 1,130 | | | (5,157) | | | 2,922 | Purchases | | | 9,807 | | | 6,995 | | | 42,392 | | | 15,093 | Sales / Calls / Maturities | | | (1,346) | | | (8,149) | | | (6,577) | | | (11,630) | Transfers into Level 3 | | | — | | | — | | | — | | | — | Transfers out of Level 3 | | | — | | | — | | | — | | | — | Balance as of September 30, | | $ | 149,219 | | $ | 101,510 | | $ | 149,219 | | $ | 101,510 | Change in unrealized gains (losses) during the period for Level 3 assets held at period-end - included in other comprehensive earnings (loss) | | $ | (3,826) | | $ | 1,244 | | $ | (5,160) | | $ | 2,899 |
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| Schedule of Contractual Maturity of Securities |
| | | | | | | | | September 30, 2026 | (in thousands) | | Amortized Cost | | Fair Value | Due in one year or less | | $ | 129,726 | | $ | 128,624 | Due after one year through five years | | | 831,022 | | | 800,568 | Due after five years through 10 years | | | 926,854 | | | 873,702 | Due after 10 years | | | 544,412 | | | 435,935 | ABS/CMBS/MBS* | | | 1,460,792 | | | 1,362,140 | Total available-for-sale | | $ | 3,892,806 | | $ | 3,600,969 |
* | Asset-backed, commercial mortgage-backed and mortgage-backed securities |
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| Schedule of Amortized Cost and Fair Value of Available-for-sale Securities |
| | | | | | | | | | | | | | | | | | September 30, 2026 | | | Cost or | | Allowance | | Gross | | Gross | | | | | | Amortized | | for Credit | | Unrealized | | Unrealized | | Fair | (in thousands) | | Cost | | Losses | | Gains | | Losses | | Value | U.S. government | | $ | 255,418 | | $ | — | | $ | — | | $ | (9,445) | | $ | 245,973 | U.S. agency | | | 25,845 | | | — | | | 6 | | | (964) | | | 24,887 | Non-U.S. government & agency | | | 16,886 | | | — | | | — | | | (1,255) | | | 15,631 | Agency MBS | | | 643,916 | | | — | | | 71 | | | (63,742) | | | 580,245 | ABS/CMBS/MBS* | | | 816,876 | | | (197) | | | 669 | | | (35,453) | | | 781,895 | Corporate | | | 1,715,017 | | | (325) | | | 1,462 | | | (92,200) | | | 1,623,954 | Municipal | | | 418,848 | | | — | | | 36 | | | (90,500) | | | 328,384 | Total Fixed Income | | $ | 3,892,806 | | $ | (522) | | $ | 2,244 | | $ | (293,559) | | $ | 3,600,969 | | | | | | | | | | | | | | | | | | | December 31, 2025 | | | Cost or | | Allowance | | Gross | | Gross | | | | | | Amortized | | for Credit | | Unrealized | | Unrealized | | Fair | (in thousands) | | Cost | | Losses | | Gains | | Losses | | Value | U.S. government | | $ | 331,233 | | $ | — | | $ | 4,909 | | $ | (919) | | $ | 335,223 | U.S. agency | | | 37,379 | | | — | | | 677 | | | (129) | | | 37,927 | Non-U.S. government & agency | | | 13,831 | | | — | | | 274 | | | (558) | | | 13,547 | Agency MBS | | | 634,349 | | | — | | | 4,718 | | | (28,392) | | | 610,675 | ABS/CMBS/MBS* | | | 685,126 | | | (470) | | | 3,640 | | | (15,312) | | | 672,984 | Corporate | | | 1,502,843 | | | (358) | | | 16,951 | | | (27,930) | | | 1,491,506 | Municipal | | | 437,601 | | | — | | | 1,068 | | | (67,195) | | | 371,474 | Total Fixed Income | | $ | 3,642,362 | | $ | (828) | | $ | 32,237 | | $ | (140,435) | | $ | 3,533,336 |
* | Non-agency asset-backed, commercial mortgage-backed and mortgage-backed securities |
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| Schedule of Debt Securities Available-for-sale Allowance for Credit Loss |
| | | | | | | | | | | | | | | Three Months Ended September 30, | | Nine Months Ended September 30, | (in thousands) | | 2026 | | 2025 | | 2026 | | 2025 | Beginning balance | | $ | 463 | | $ | 245 | | $ | 828 | | $ | 197 | Increase to allowance from securities for which credit losses were not previously recorded | | | 118 | | | 717 | | | 240 | | | 720 | Reduction from securities sold during the period | | | — | | | — | | | (67) | | | — | Reductions from intent to sell securities | | | — | | | — | | | (180) | | | — | Net increase (decrease) from securities that had an allowance at the beginning of the period | | | (59) | | | (63) | | | (299) | | | (18) | Balance as of September 30, | | $ | 522 | | $ | 899 | | $ | 522 | | $ | 899 |
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| Schedule of Securities in an Unrealized Loss Position Segregated by Type and Length of Time in an Unrealized Loss Position |
| | | | | | | | | | | | | | | | | | | | | September 30, 2026 | | December 31, 2025 | (in thousands) | | < 12 Mos. | | 12 Mos. &
Greater | | Total | | < 12 Mos. | | 12 Mos. &
Greater | | Total | U.S. government | | | | | | | | | | | | | | | | | | | Fair value | | $ | 212,038 | | $ | 33,934 | | $ | 245,972 | | $ | 8,610 | | $ | 80,088 | | $ | 88,698 | Amortized cost | | | 220,509 | | | 34,908 | | | 255,417 | | | 8,620 | | | 80,997 | | | 89,617 | Unrealized loss | | $ | (8,471) | | $ | (974) | | $ | (9,445) | | $ | (10) | | $ | (909) | | $ | (919) | U.S. agency | | | | | | | | | | | | | | | | | | | Fair value | | $ | 14,686 | | $ | 7,413 | | $ | 22,099 | | $ | — | | $ | 19,797 | | $ | 19,797 | Amortized cost | | | 15,554 | | | 7,509 | | | 23,063 | | | — | | | 19,926 | | | 19,926 | Unrealized loss | | $ | (868) | | $ | (96) | | $ | (964) | | $ | — | | $ | (129) | | $ | (129) | Non-U.S. government | | | | | | | | | | | | | | | | | | | Fair value | | $ | 11,504 | | $ | 4,127 | | $ | 15,631 | | $ | — | | $ | 4,244 | | $ | 4,244 | Amortized cost | | | 12,083 | | | 4,803 | | | 16,886 | | | — | | | 4,802 | | | 4,802 | Unrealized Loss | | $ | (579) | | $ | (676) | | $ | (1,255) | | $ | — | | $ | (558) | | $ | (558) | Agency MBS | | | | | | | | | | | | | | | | | | | Fair value | | $ | 398,264 | | $ | 173,317 | | $ | 571,581 | | $ | 34,783 | | $ | 239,581 | | $ | 274,364 | Amortized cost | | | 423,723 | | | 211,600 | | | 635,323 | | | 34,917 | | | 267,839 | | | 302,756 | Unrealized loss | | $ | (25,459) | | $ | (38,283) | | $ | (63,742) | | $ | (134) | | $ | (28,258) | | $ | (28,392) | ABS/CMBS/MBS* | | | | | | | | | | | | | | | | | | | Fair value | | $ | 508,786 | | $ | 134,151 | | $ | 642,937 | | $ | 110,600 | | $ | 142,903 | | $ | 253,503 | Amortized cost | | | 524,822 | | | 153,568 | | | 678,390 | | | 110,826 | | | 157,989 | | | 268,815 | Unrealized loss | | $ | (16,036) | | $ | (19,417) | | $ | (35,453) | | $ | (226) | | $ | (15,086) | | $ | (15,312) | Corporate | | | | | | | | | | | | | | | | | | | Fair value | | $ | 1,095,945 | | $ | 393,497 | | $ | 1,489,442 | | $ | 146,177 | | $ | 545,897 | | $ | 692,074 | Amortized cost | | | 1,145,126 | | | 436,516 | | | 1,581,642 | | | 148,444 | | | 571,560 | | | 720,004 | Unrealized loss | | $ | (49,181) | | $ | (43,019) | | $ | (92,200) | | $ | (2,267) | | $ | (25,663) | | $ | (27,930) | Municipal | | | | | | | | | | | | | | | | | | | Fair value | | $ | 52,372 | | $ | 270,378 | | $ | 322,750 | | $ | 3,759 | | $ | 324,235 | | $ | 327,994 | Amortized cost | | | 55,873 | | | 357,377 | | | 413,250 | | | 3,789 | | | 391,400 | | | 395,189 | Unrealized loss | | $ | (3,501) | | $ | (86,999) | | $ | (90,500) | | $ | (30) | | $ | (67,165) | | $ | (67,195) | Total fixed income | | | | | | | | | | | | | | | | | | | Fair value | | $ | 2,293,595 | | $ | 1,016,817 | | $ | 3,310,412 | | $ | 303,929 | | $ | 1,356,745 | | $ | 1,660,674 | Amortized cost | | | 2,397,690 | | | 1,206,281 | | | 3,603,971 | | | 306,596 | | | 1,494,513 | | | 1,801,109 | Unrealized loss | | $ | (104,095) | | $ | (189,464) | | $ | (293,559) | | $ | (2,667) | | $ | (137,768) | | $ | (140,435) |
* | Non-agency asset-backed, commercial mortgage-backed and mortgage-backed securities |
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| Schedule of Credit Quality Indicators for Investments in Unrealized Loss Positions |
| | | | | | | | | | | | | | | | | | | Equivalent | | Equivalent | | (dollars in thousands) | | | | NAIC | | S&P | | Moody’s | | Amortized | | | | | Unrealized | | Percent | | Rating | | Rating | | Rating | | Cost | | Fair Value | | Loss | | to Total | | 1 | | AAA/AA/A | | Aaa/Aa/A | | $ | 2,869,804 | | $ | 2,618,245 | | $ | (251,559) | | 85.7 | % | 2 | | BBB | | Baa | | | 627,493 | | | 590,688 | | | (36,805) | | 12.5 | % | 3 | | BB | | Ba | | | 69,396 | | | 66,741 | | | (2,655) | | 0.9 | % | 4 | | B | | B | | | 32,972 | | | 31,328 | | | (1,644) | | 0.6 | % | 5 | | CCC | | Caa | | | 3,452 | | | 2,629 | | | (823) | | 0.3 | % | 6 | | CC or lower | | Ca or lower | | | 854 | | | 781 | | | (73) | | 0.0 | % | | | | | Total | | $ | 3,603,971 | | $ | 3,310,412 | | $ | (293,559) | | 100.0 | % |
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