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Summary Of Investments Other Than Investments In Related Parties (Details) - USD ($) $ in Thousands | Dec. 31, 2021 | Dec. 31, 2020
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SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | $ 4,805,522 | $ 4,460,115
Fair Value | 5,142,589 | 4,729,270
Amounts in the Balance Sheet | 5,142,589 | 4,729,270
Fixed maturity securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 3,909,780 | 3,388,418
Fair Value | 4,031,523 | 3,549,810
Amounts in the Balance Sheet | 4,031,523 | 3,549,810
U.S. government bonds |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 13,082 | 13,756
Fair Value | 13,085 | 13,816
Amounts in the Balance Sheet | 13,085 | 13,816
Municipal securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 2,715,578 | 2,632,559
Fair Value | 2,843,221 | 2,791,212
Amounts in the Balance Sheet | 2,843,221 | 2,791,212
Mortgage-backed securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 137,384 | 91,527
Fair Value | 137,002 | 93,264
Amounts in the Balance Sheet | 137,002 | 93,264
Corporate securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 529,377 | 240,486
Fair Value | 523,853 | 241,366
Amounts in the Balance Sheet | 523,853 | 241,366
Collateralized loan obligations |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 312,928 | 256,558
Fair Value | 314,153 | 256,891
Amounts in the Balance Sheet | 314,153 | 256,891
Other asset-backed securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 201,431 | 153,532
Fair Value | 200,209 | 153,261
Amounts in the Balance Sheet | 200,209 | 153,261
Equity securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 754,536 | 695,150
Fair Value | 970,939 | 803,851
Amounts in the Balance Sheet | 970,939 | 803,851
Common stock |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 561,381 | 563,394
Fair Value | 797,024 | 691,782
Amounts in the Balance Sheet | 797,024 | 691,782
Non-redeemable preferred stock |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 64,429 | 31,430
Fair Value | 65,501 | 32,660
Amounts in the Balance Sheet | 65,501 | 32,660
Private Equity Funds Net Asset Value |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 128,726 | 100,326
Fair Value | 108,414 | 79,409
Amounts in the Balance Sheet | 108,414 | 79,409
Short-term investments |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 141,206 | 376,547
Fair Value | 140,127 | 375,609
Amounts in the Balance Sheet | $ 140,127 | $ 375,609

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