Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Sep. 30, 2022 | Dec. 31, 2021 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | $ 3,897,859 | $ 4,031,523 |
Equity securities: | 684,335 | 970,939 |
Fair Value, Measurements, Recurring | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 3,897,859 | 4,031,523 |
Equity securities: | 684,335 | 970,939 |
Short-term investments: | 100,621 | 140,127 |
Assets, fair value disclosure | 4,682,815 | 5,142,589 |
Liabilities | 169 | 301 |
Fair Value, Measurements, Recurring | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 59,327 | 13,085 |
Equity securities: | 537,455 | 797,024 |
Short-term investments: | 100,621 | 124,379 |
Assets, fair value disclosure | 697,403 | 934,488 |
Liabilities | 169 | 301 |
Fair Value, Measurements, Recurring | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 3,838,532 | 4,018,438 |
Equity securities: | 54,042 | 65,501 |
Short-term investments: | 0 | 15,748 |
Assets, fair value disclosure | 3,892,574 | 4,099,687 |
Liabilities | 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 |
Assets, fair value disclosure | 0 | 0 |
Liabilities | 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: | 69,363 | 13,085 |
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: | 59,327 | 13,085 |
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: | 10,036 | 0 |
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: | 2,688,727 | 2,843,221 |
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: | 2,688,727 | 2,843,221 |
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: | 165,208 | 137,002 |
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: | 165,208 | 137,002 |
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: | 510,811 | 523,853 |
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: | 510,811 | 523,853 |
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: | 285,360 | 314,153 |
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: | 285,360 | 314,153 |
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: | 178,390 | 200,209 |
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: | 178,390 | 200,209 |
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: | 537,455 | 797,024 |
Fair Value, Measurements, Recurring | Common stock | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Equity securities: | 537,455 | 797,024 |
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: | 54,042 | 65,501 |
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: | 54,042 | 65,501 |
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: | 92,838 | 108,414 |
Fair Value, Measurements, Recurring | Short-term bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 15,488 | 17,201 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 15,488 | 1,453 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 0 | 15,748 |
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: | 85,094 | 122,917 |
Fair Value, Measurements, Recurring | Money market instruments | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 85,094 | 122,917 |
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: | 39 | 9 |
Fair Value, Measurements, Recurring | Other | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 39 | 9 |
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] | | |
Derivative liability | 169 | 301 |
Fair Value, Measurements, Recurring | Options sold | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative liability | 169 | 301 |
Fair Value, Measurements, Recurring | Options sold | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative liability | 0 | 0 |
Fair Value, Measurements, Recurring | Options sold | Level 3 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative liability | $ 0 | $ 0 |