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Summary Of Investments Other Than Investments In Related Parties (Details) - USD ($) $ in Thousands | Dec. 31, 2022 | Dec. 31, 2021
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SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | $ 5,019,561 | $ 4,805,522
Fair Value | 4,910,800 | 5,142,589
Amounts in the Balance Sheet | 4,910,800 | 5,142,589
Fixed maturity securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 4,226,790 | 3,909,780
Fair Value | 4,088,311 | 4,031,523
Amounts in the Balance Sheet | 4,088,311 | 4,031,523
U.S. government bonds |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 159,256 | 13,082
Fair Value | 158,607 | 13,085
Amounts in the Balance Sheet | 158,607 | 13,085
Municipal securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 2,794,476 | 2,715,578
Fair Value | 2,737,183 | 2,843,221
Amounts in the Balance Sheet | 2,737,183 | 2,843,221
Mortgage-backed securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 184,936 | 137,384
Fair Value | 166,260 | 137,002
Amounts in the Balance Sheet | 166,260 | 137,002
Corporate securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 607,945 | 529,377
Fair Value | 569,553 | 523,853
Amounts in the Balance Sheet | 569,553 | 523,853
Collateralized loan obligations |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 332,859 | 312,928
Fair Value | 320,252 | 314,153
Amounts in the Balance Sheet | 320,252 | 314,153
Other asset-backed securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 147,318 | 201,431
Fair Value | 136,456 | 200,209
Amounts in the Balance Sheet | 136,456 | 200,209
Equity securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 668,843 | 754,536
Fair Value | 699,552 | 970,939
Amounts in the Balance Sheet | 699,552 | 970,939
Common stock |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 463,940 | 561,381
Fair Value | 558,169 | 797,024
Amounts in the Balance Sheet | 558,169 | 797,024
Preferred stock |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 64,686 | 64,429
Fair Value | 51,236 | 65,501
Amounts in the Balance Sheet | 51,236 | 65,501
Private Equity Funds Net Asset Value |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 140,217 | 128,726
Fair Value | 90,147 | 108,414
Amounts in the Balance Sheet | 90,147 | 108,414
Short-term investments |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 123,928 | 141,206
Fair Value | 122,937 | 140,127
Amounts in the Balance Sheet | $ 122,937 | $ 140,127

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