Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Jun. 30, 2023 | Dec. 31, 2022 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | $ 4,094,703 | $ 4,088,311 |
Equity securities: | 670,491 | 699,552 |
Note receivable | 9,925 | 0 |
Fair Value, Measurements, Recurring | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 4,094,703 | 4,088,311 |
Equity securities: | 670,491 | 699,552 |
Short-term investments: | 189,991 | 122,937 |
Note receivable | 9,925 | |
Assets, fair value disclosure | 4,965,110 | 4,910,800 |
Options sold | 817 | 162 |
Fair Value, Measurements, Recurring | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 116,762 | 103,519 |
Equity securities: | 531,788 | 558,169 |
Short-term investments: | 188,012 | 114,699 |
Note receivable | 0 | |
Assets, fair value disclosure | 836,562 | 776,387 |
Options sold | 817 | 162 |
Fair Value, Measurements, Recurring | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 3,977,941 | 3,984,792 |
Equity securities: | 51,722 | 51,236 |
Short-term investments: | 1,979 | 8,238 |
Note receivable | 9,925 | |
Assets, fair value disclosure | 4,041,567 | 4,044,266 |
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 | |
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: | 159,534 | 158,607 |
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: | 116,762 | 103,519 |
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: | 42,772 | 55,088 |
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: | 2,715,436 | 2,737,183 |
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: | 2,715,436 | 2,737,183 |
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: | 156,650 | 166,260 |
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: | 156,650 | 166,260 |
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: | 594,761 | 569,553 |
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: | 594,761 | 569,553 |
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: | 362,220 | 320,252 |
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: | 362,220 | 320,252 |
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: | 106,102 | 136,456 |
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: | 106,102 | 136,456 |
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: | 531,788 | 558,169 |
Fair Value, Measurements, Recurring | Common stock | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Equity securities: | 531,788 | 558,169 |
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: | 51,722 | 51,236 |
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: | 51,722 | 51,236 |
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: | 86,981 | 90,147 |
Fair Value, Measurements, Recurring | Short-term bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 55,099 | 59,876 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 53,120 | 51,638 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 1,979 | 8,238 |
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: | 134,852 | 63,021 |
Fair Value, Measurements, Recurring | Money market instruments | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 134,852 | 63,021 |
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: | 40 | 40 |
Fair Value, Measurements, Recurring | Other | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 40 | 40 |
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 | 817 | 162 |
Fair Value, Measurements, Recurring | Options sold | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Options sold | 817 | 162 |
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 |