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Investments (Investments Held in a Loss Position) (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Fair value |  |
Fair Value | $ 1,541,516 | $ 212,934
Less than 12 Months, Fair Value | 1,486,475 | 191,081
More than 12 Months, Fair Value | 55,041 | 21,853
Unrealized Loss |  |
Unrealized Loss | 14,318 | 3,428
Less than 12 Months, Unrealized Loss | 12,712 | 3,099
More than 12 Months, Unrealized Loss | 1,606 | 329
U.S. Treasury obligations |  |
Fair value |  |
Fair Value | 162,063 | 14,390
Less than 12 Months, Fair Value | 157,445 | 14,390
More than 12 Months, Fair Value | 4,618 | 0
Unrealized Loss |  |
Unrealized Loss | 672 | 23
Less than 12 Months, Unrealized Loss | 582 | 23
More than 12 Months, Unrealized Loss | 90 | 0
U.S. Government-sponsored enterprise obligations |  |
Fair value |  |
Fair Value | 14,422 |
Less than 12 Months, Fair Value | 14,422 |
More than 12 Months, Fair Value | 0 |
Unrealized Loss |  |
Unrealized Loss | 98 |
Less than 12 Months, Unrealized Loss | 98 |
More than 12 Months, Unrealized Loss | 0 |
State and municipal bonds |  |
Fair value |  |
Fair Value | 194,740 | 6,416
Less than 12 Months, Fair Value | 192,610 | 6,416
More than 12 Months, Fair Value | 2,130 | 0
Unrealized Loss |  |
Unrealized Loss | 1,559 | 39
Less than 12 Months, Unrealized Loss | 1,467 | 39
More than 12 Months, Unrealized Loss | 92 | 0
Corporate debt |  |
Fair value |  |
Fair Value | 637,694 | 94,695
Less than 12 Months, Fair Value | 607,003 | 79,436
More than 12 Months, Fair Value | 30,691 | 15,259
Unrealized Loss |  |
Unrealized Loss | 6,923 | 1,302
Less than 12 Months, Unrealized Loss | 6,134 | 1,020
More than 12 Months, Unrealized Loss | 789 | 282
Residential mortgage-backed securities |  |
Fair value |  |
Fair Value | 284,636 | 34,928
Less than 12 Months, Fair Value | 276,253 | 34,509
More than 12 Months, Fair Value | 8,383 | 419
Unrealized Loss |  |
Unrealized Loss | 2,972 | 382
Less than 12 Months, Unrealized Loss | 2,732 | 381
More than 12 Months, Unrealized Loss | 240 | 1
Agency commercial mortgage-backed securities |  |
Fair value |  |
Fair Value | 4,040 |
Less than 12 Months, Fair Value | 4,040 |
More than 12 Months, Fair Value | 0 |
Unrealized Loss |  |
Unrealized Loss | 49 |
Less than 12 Months, Unrealized Loss | 49 |
More than 12 Months, Unrealized Loss | 0 |
Other commercial mortgage-backed securities |  |
Fair value |  |
Fair Value | 77,254 | 18,766
Less than 12 Months, Fair Value | 72,541 | 18,480
More than 12 Months, Fair Value | 4,713 | 286
Unrealized Loss |  |
Unrealized Loss | 1,116 | 940
Less than 12 Months, Unrealized Loss | 783 | 935
More than 12 Months, Unrealized Loss | 333 | 5
Other asset-backed securities |  |
Fair value |  |
Fair Value | 166,667 | 43,739
Less than 12 Months, Fair Value | 162,161 | 37,850
More than 12 Months, Fair Value | 4,506 | 5,889
Unrealized Loss |  |
Unrealized Loss | 929 | 742
Less than 12 Months, Unrealized Loss | 867 | 701
More than 12 Months, Unrealized Loss | $ 62 | $ 41

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