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Investments - Securities in an Unrealized Loss Position Segregated by Type and Length of Time in an Unrealized Loss Position (Details) - USD ($) $ in Thousands | Mar. 31, 2026 | Dec. 31, 2025
--- | --- | ---
Fair value |  |
Less than 12 months | $ 1,165,564 | $ 303,929
12 months and greater | 1,187,480 | 1,356,745
Total Fair Value | 2,353,044 | 1,660,674
Amortized Cost |  |
Amortized cost, less than 12 months | 1,178,696 | 306,596
12 months and greater | 1,330,557 | 1,494,513
Total Amortized Cost | 2,509,253 | 1,801,109
Unrealized Loss |  |
Less than 12 months | (13,132) | (2,667)
12 months and greater | (143,077) | (137,768)
Total Unrealized Loss | (156,209) | (140,435)
U.S. government |  |
Fair value |  |
Less than 12 months | 13,965 | 8,610
12 months and greater | 61,176 | 80,088
Total Fair Value | 75,141 | 88,698
Amortized Cost |  |
Amortized cost, less than 12 months | 14,113 | 8,620
12 months and greater | 62,084 | 80,997
Total Amortized Cost | 76,197 | 89,617
Unrealized Loss |  |
Less than 12 months | (148) | (10)
12 months and greater | (908) | (909)
Total Unrealized Loss | (1,056) | (919)
U.S. Agency |  |
Fair value |  |
Less than 12 months | 7,741 |
12 months and greater | 8,934 | 19,797
Total Fair Value | 16,675 | 19,797
Amortized Cost |  |
Amortized cost, less than 12 months | 7,923 |
12 months and greater | 9,008 | 19,926
Total Amortized Cost | 16,931 | 19,926
Unrealized Loss |  |
Less than 12 months | (182) |
12 months and greater | (74) | (129)
Total Unrealized Loss | (256) | (129)
Non-U.S. government |  |
Fair value |  |
Less than 12 months | 7,210 |
12 months and greater | 4,204 | 4,244
Total Fair Value | 11,414 | 4,244
Amortized Cost |  |
Amortized cost, less than 12 months | 7,310 |
12 months and greater | 4,802 | 4,802
Total Amortized Cost | 12,112 | 4,802
Unrealized Loss |  |
Less than 12 months | (100) |
12 months and greater | (598) | (558)
Total Unrealized Loss | (698) | (558)
Agency MBS |  |
Fair value |  |
Less than 12 months | 238,880 | 34,783
12 months and greater | 197,811 | 239,581
Total Fair Value | 436,691 | 274,364
Amortized Cost |  |
Amortized cost, less than 12 months | 241,035 | 34,917
12 months and greater | 226,470 | 267,839
Total Amortized Cost | 467,505 | 302,756
Unrealized Loss |  |
Less than 12 months | (2,155) | (134)
12 months and greater | (28,659) | (28,258)
Total Unrealized Loss | (30,814) | (28,392)
ABS/CMBS/MBS |  |
Fair value |  |
Less than 12 months | 354,186 | 110,600
12 months and greater | 136,541 | 142,903
Total Fair Value | 490,727 | 253,503
Amortized Cost |  |
Amortized cost, less than 12 months | 356,597 | 110,826
12 months and greater | 151,784 | 157,989
Total Amortized Cost | 508,381 | 268,815
Unrealized Loss |  |
Less than 12 months | (2,411) | (226)
12 months and greater | (15,243) | (15,086)
Total Unrealized Loss | (17,654) | (15,312)
Corporate |  |
Fair value |  |
Less than 12 months | 517,300 | 146,177
12 months and greater | 477,322 | 545,897
Total Fair Value | 994,622 | 692,074
Amortized Cost |  |
Amortized cost, less than 12 months | 525,093 | 148,444
12 months and greater | 508,114 | 571,560
Total Amortized Cost | 1,033,207 | 720,004
Unrealized Loss |  |
Less than 12 months | (7,793) | (2,267)
12 months and greater | (30,792) | (25,663)
Total Unrealized Loss | (38,585) | (27,930)
Municipal |  |
Fair value |  |
Less than 12 months | 26,282 | 3,759
12 months and greater | 301,492 | 324,235
Total Fair Value | 327,774 | 327,994
Amortized Cost |  |
Amortized cost, less than 12 months | 26,625 | 3,789
12 months and greater | 368,295 | 391,400
Total Amortized Cost | 394,920 | 395,189
Unrealized Loss |  |
Less than 12 months | (343) | (30)
12 months and greater | (66,803) | (67,165)
Total Unrealized Loss | $ (67,146) | $ (67,195)

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