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 |