Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Jun. 30, 2024 | Dec. 31, 2023 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | $ 4,661,761 | $ 4,319,336 |
Equity securities | 815,924 | 730,693 |
Note receivable | 9,803 | 9,974 |
Fair Value, Measurements, Recurring | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 4,661,761 | 4,319,336 |
Equity securities | 815,924 | 730,693 |
Short-term investments | 147,865 | 178,491 |
Note receivable | 9,803 | 9,974 |
Assets, fair value disclosure | 5,635,353 | 5,238,494 |
Total liabilities at fair value | 663 | 1,955 |
Fair Value, Measurements, Recurring | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 136,291 | 123,182 |
Equity securities | 678,705 | 597,888 |
Short-term investments | 146,240 | 176,653 |
Note receivable | 0 | 0 |
Assets, fair value disclosure | 961,236 | 897,723 |
Total liabilities at fair value | 663 | 1,955 |
Fair Value, Measurements, Recurring | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 4,525,470 | 4,196,154 |
Equity securities | 45,131 | 51,563 |
Short-term investments | 1,625 | 1,838 |
Note receivable | 9,803 | 9,974 |
Assets, fair value disclosure | 4,582,029 | 4,259,529 |
Total liabilities at fair value | 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 |
Total liabilities at fair value | 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: | 195,579 | 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: | 136,291 | 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: | 59,288 | 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: | 2,860,186 | 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: | 2,860,186 | 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: | 220,341 | 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: | 220,341 | 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: | 741,587 | 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: | 741,587 | 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: | 541,199 | 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: | 541,199 | 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: | 102,869 | 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: | 102,869 | 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 | 678,705 | 597,888 |
Fair Value, Measurements, Recurring | Common stock | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Equity securities | 678,705 | 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 | 45,131 | 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 | 45,131 | 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 | 92,088 | 81,242 |
Fair Value, Measurements, Recurring | Short-term bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments | 11,893 | 13,853 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments | 10,268 | 12,015 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments | 1,625 | 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 | 135,928 | 164,595 |
Fair Value, Measurements, Recurring | Money market instruments | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments | 135,928 | 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 | 44 | 43 |
Fair Value, Measurements, Recurring | Other | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments | 44 | 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 | 663 | 1,955 |
Fair Value, Measurements, Recurring | Options sold | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Options sold | 663 | 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 |