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Summary Of Investments Other Than Investments In Related Parties (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
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SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | $ 5,229,297 | $ 5,019,561
Fair Value | 5,228,520 | 4,910,800
Amounts in the Balance Sheet | 5,228,520 | 4,910,800
Fixed maturity securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 4,394,983 | 4,226,790
Fair Value | 4,319,336 | 4,088,311
Amounts in the Balance Sheet | 4,319,336 | 4,088,311
U.S. government bonds and agencies |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 174,903 | 159,256
Fair Value | 174,450 | 158,607
Amounts in the Balance Sheet | 174,450 | 158,607
Municipal securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 2,797,971 | 2,794,476
Fair Value | 2,777,258 | 2,737,183
Amounts in the Balance Sheet | 2,777,258 | 2,737,183
Mortgage-backed securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 201,727 | 184,936
Fair Value | 186,887 | 166,260
Amounts in the Balance Sheet | 186,887 | 166,260
Corporate securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 626,723 | 607,945
Fair Value | 599,630 | 569,553
Amounts in the Balance Sheet | 599,630 | 569,553
Collateralized loan obligations |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 486,984 | 332,859
Fair Value | 484,947 | 320,252
Amounts in the Balance Sheet | 484,947 | 320,252
Other asset-backed securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 106,675 | 147,318
Fair Value | 96,164 | 136,456
Amounts in the Balance Sheet | 96,164 | 136,456
Equity securities |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 654,939 | 668,843
Fair Value | 730,693 | 699,552
Amounts in the Balance Sheet | 730,693 | 699,552
Common stock |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 497,543 | 463,940
Fair Value | 597,888 | 558,169
Amounts in the Balance Sheet | 597,888 | 558,169
Non-redeemable preferred stock |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 64,860 | 64,686
Fair Value | 51,563 | 51,236
Amounts in the Balance Sheet | 51,563 | 51,236
Private equity funds measured at net asset value |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 92,536 | 140,217
Fair Value | 81,242 | 90,147
Amounts in the Balance Sheet | 81,242 | 90,147
Short-term investments |  |
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items] |  |
Cost | 179,375 | 123,928
Fair Value | 178,491 | 122,937
Amounts in the Balance Sheet | $ 178,491 | $ 122,937

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