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Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | $ 4,489,552 | $ 4,319,336
Equity securities | 801,108 | 730,693
Note receivable | 9,818 | 9,974
Fair Value, Measurements, Recurring |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 4,489,552 | 4,319,336
Equity securities | 801,108 | 730,693
Short-term investments | 162,466 | 178,491
Note receivable | 9,818 | 9,974
Assets, fair value disclosure | 5,462,944 | 5,238,494
Options sold | 1,928 | 1,955
Fair Value, Measurements, Recurring | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 141,161 | 123,182
Equity securities | 672,106 | 597,888
Short-term investments | 160,636 | 176,653
Note receivable | 0 | 0
Assets, fair value disclosure | 973,903 | 897,723
Options sold | 1,928 | 1,955
Fair Value, Measurements, Recurring | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 4,348,391 | 4,196,154
Equity securities | 45,241 | 51,563
Short-term investments | 1,830 | 1,838
Note receivable | 9,818 | 9,974
Assets, fair value disclosure | 4,405,280 | 4,259,529
Options sold | 0 | 0
Fair Value, Measurements, Recurring | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Equity securities | 0 | 0
Short-term investments | 0 | 0
Note receivable | 0 | 0
Assets, fair value disclosure | 0 | 0
Options sold | 0 | 0
Fair Value, Measurements, Recurring | U.S. government bonds and agencies |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 200,344 | 174,450
Fair Value, Measurements, Recurring | U.S. government bonds and agencies | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 141,161 | 123,182
Fair Value, Measurements, Recurring | U.S. government bonds and agencies | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 59,183 | 51,268
Fair Value, Measurements, Recurring | U.S. government bonds and agencies | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Municipal securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 2,795,677 | 2,777,258
Fair Value, Measurements, Recurring | Municipal securities | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Municipal securities | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 2,795,677 | 2,777,258
Fair Value, Measurements, Recurring | Municipal securities | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Mortgage-backed securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 193,040 | 186,887
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 193,040 | 186,887
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Corporate securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 706,210 | 599,630
Fair Value, Measurements, Recurring | Corporate securities | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Corporate securities | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 706,210 | 599,630
Fair Value, Measurements, Recurring | Corporate securities | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Collateralized loan obligations |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 495,523 | 484,947
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 495,523 | 484,947
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Other asset-backed securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 98,758 | 96,164
Fair Value, Measurements, Recurring | Other asset-backed securities | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Other asset-backed securities | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 98,758 | 96,164
Fair Value, Measurements, Recurring | Other asset-backed securities | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Fixed maturity securities: | 0 | 0
Fair Value, Measurements, Recurring | Common stock |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 672,106 | 597,888
Fair Value, Measurements, Recurring | Common stock | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 672,106 | 597,888
Fair Value, Measurements, Recurring | Common stock | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 0 | 0
Fair Value, Measurements, Recurring | Common stock | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 0 | 0
Fair Value, Measurements, Recurring | Non-redeemable preferred stock |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 45,241 | 51,563
Fair Value, Measurements, Recurring | Non-redeemable preferred stock | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 0 | 0
Fair Value, Measurements, Recurring | Non-redeemable preferred stock | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 45,241 | 51,563
Fair Value, Measurements, Recurring | Non-redeemable preferred stock | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 0 | 0
Fair Value, Measurements, Recurring | Private equity funds measured at net asset value |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Equity securities | 83,761 | 81,242
Fair Value, Measurements, Recurring | Short-term bonds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 13,970 | 13,853
Fair Value, Measurements, Recurring | Short-term bonds | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 12,140 | 12,015
Fair Value, Measurements, Recurring | Short-term bonds | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 1,830 | 1,838
Fair Value, Measurements, Recurring | Short-term bonds | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 0 | 0
Fair Value, Measurements, Recurring | Money market instruments |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 148,449 | 164,595
Fair Value, Measurements, Recurring | Money market instruments | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 148,449 | 164,595
Fair Value, Measurements, Recurring | Money market instruments | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 0 | 0
Fair Value, Measurements, Recurring | Money market instruments | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 0 | 0
Fair Value, Measurements, Recurring | Other |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 47 | 43
Fair Value, Measurements, Recurring | Other | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 47 | 43
Fair Value, Measurements, Recurring | Other | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 0 | 0
Fair Value, Measurements, Recurring | Other | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Short-term investments | 0 | 0
Fair Value, Measurements, Recurring | Options sold |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Options sold | 1,928 | 1,955
Fair Value, Measurements, Recurring | Options sold | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Options sold | 1,928 | 1,955
Fair Value, Measurements, Recurring | Options sold | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Options sold | 0 | 0
Fair Value, Measurements, Recurring | Options sold | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Options sold | $ 0 | $ 0

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- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. 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Data Type: | na
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