Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Jun. 30, 2022 | Dec. 31, 2021 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | $ 3,878,684 | $ 4,031,523 |
Equity securities: | 782,802 | 970,939 |
Fair Value, Measurements, Recurring | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 3,878,684 | 4,031,523 |
Equity securities: | 782,802 | 970,939 |
Short-term investments: | 172,130 | 140,127 |
Assets, fair value disclosure | 4,833,616 | 5,142,589 |
Liabilities | 122 | 301 |
Fair Value, Measurements, Recurring | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 14,026 | 13,085 |
Equity securities: | 635,185 | 797,024 |
Short-term investments: | 157,466 | 124,379 |
Assets, fair value disclosure | 806,677 | 934,488 |
Liabilities | 122 | 301 |
Fair Value, Measurements, Recurring | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 3,864,658 | 4,018,438 |
Equity securities: | 57,721 | 65,501 |
Short-term investments: | 14,664 | 15,748 |
Assets, fair value disclosure | 3,937,043 | 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 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 14,026 | 13,085 |
Fair Value, Measurements, Recurring | U.S. government bonds | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 14,026 | 13,085 |
Fair Value, Measurements, Recurring | U.S. government bonds | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Fixed maturity securities: | 0 | 0 |
Fair Value, Measurements, Recurring | U.S. government bonds | 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: | 2,710,968 | 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: | 2,710,968 | 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: | 156,074 | 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: | 156,074 | 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: | 522,529 | 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: | 522,529 | 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: | 301,046 | 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: | 301,046 | 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: | 174,041 | 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: | 174,041 | 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: | 635,185 | 797,024 |
Fair Value, Measurements, Recurring | Common stock | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Equity securities: | 635,185 | 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: | 57,721 | 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: | 57,721 | 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: | 89,896 | 108,414 |
Fair Value, Measurements, Recurring | Short-term bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 11,979 | 17,201 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 795 | 1,453 |
Fair Value, Measurements, Recurring | Short-term bonds | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 11,184 | 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: | 160,123 | 122,917 |
Fair Value, Measurements, Recurring | Money market instruments | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 156,643 | 122,917 |
Fair Value, Measurements, Recurring | Money market instruments | Level 2 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 3,480 | 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: | 28 | 9 |
Fair Value, Measurements, Recurring | Other | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Short-term investments: | 28 | 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 | 122 | 301 |
Fair Value, Measurements, Recurring | Options sold | Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative liability | 122 | 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 |