v3.26.1
Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities $ 5,499,834 $ 5,430,251
Equity securities 883,623 812,787
Note receivable 9,926 9,993
Fair Value, Measurements, Recurring    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 5,499,834 5,430,251
Equity securities 883,623 812,787
Short-term investments 441,841 336,992
Note receivable 9,926 9,993
Assets, fair value disclosure 6,835,224 6,590,023
Total liabilities at fair value 753 254
Fair Value, Measurements, Recurring | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 14,894 21,546
Equity securities 763,017 679,594
Short-term investments 407,841 302,992
Note receivable 0 0
Assets, fair value disclosure 1,185,752 1,004,132
Total liabilities at fair value 753 254
Fair Value, Measurements, Recurring | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 5,484,940 5,408,705
Equity securities 38,362 38,761
Short-term investments 34,000 34,000
Note receivable 9,926 9,993
Assets, fair value disclosure 5,567,228 5,491,459
Total liabilities at fair value 0 0
Fair Value, Measurements, Recurring | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total 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    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 14,894 21,546
Fair Value, Measurements, Recurring | U.S. government bonds | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 14,894 21,546
Fair Value, Measurements, Recurring | U.S. government bonds | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total 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]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Municipal securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 3,589,734 3,538,473
Fair Value, Measurements, Recurring | Municipal securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Municipal securities | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 3,589,734 3,538,473
Fair Value, Measurements, Recurring | Municipal securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 404,459 297,381
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 404,459 297,381
Fair Value, Measurements, Recurring | Mortgage-backed securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Corporate securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 693,556 751,602
Fair Value, Measurements, Recurring | Corporate securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Corporate securities | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 693,556 751,602
Fair Value, Measurements, Recurring | Corporate securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Collateralized loan obligations    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 728,368 722,794
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 728,368 722,794
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Other asset-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 68,823 98,455
Fair Value, Measurements, Recurring | Other asset-backed securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total 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]    
Total fixed maturity securities 68,823 98,455
Fair Value, Measurements, Recurring | Other asset-backed securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total fixed maturity securities 0 0
Fair Value, Measurements, Recurring | Common stock    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity securities 763,017 679,594
Fair Value, Measurements, Recurring | Common stock | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity securities 763,017 679,594
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 38,362 38,761
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 38,362 38,761
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 82,244 94,432
Fair Value, Measurements, Recurring | Short-term bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Short-term investments 34,000 34,000
Fair Value, Measurements, Recurring | Short-term bonds | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Short-term investments 0 0
Fair Value, Measurements, Recurring | Short-term bonds | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Short-term investments 34,000 34,000
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 407,809 302,978
Fair Value, Measurements, Recurring | Money market instruments | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Short-term investments 407,809 302,978
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 32 14
Fair Value, Measurements, Recurring | Other | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Short-term investments 32 14
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 753 254
Fair Value, Measurements, Recurring | Options sold | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Options sold 753 254
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