Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	$ 4,600,058	$ 4,913,378
Equity securities	588,341	879,175
Notes receivable	31,714	31,231
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	4,600,058	4,913,378
Equity securities	588,341	879,175
Short-term investments	208,143	283,817
Notes receivable	31,714	31,231
Assets, fair value disclosure	5,428,256	6,107,601
Total liabilities at fair value	387	213
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	63,469	75,874
Equity securities	449,560	741,369
Short-term investments	206,479	282,162
Notes receivable	0	0
Assets, fair value disclosure	719,508	1,099,405
Total liabilities at fair value	387	213
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	4,536,589	4,837,504
Equity securities	41,826	42,603
Short-term investments	1,664	1,655
Notes receivable	31,714	31,231
Assets, fair value disclosure	4,611,793	4,912,993
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
Notes 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]
Total fixed maturity securities	73,469	93,837
Fair Value, Measurements, Recurring | U.S. government bonds and agencies | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	63,469	75,874
Fair Value, Measurements, Recurring | U.S. government bonds and agencies | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	10,000	17,963
Fair Value, Measurements, Recurring | U.S. government bonds and agencies | 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	2,809,758	2,987,054
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	2,809,758	2,987,054
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	268,687	259,421
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	268,687	259,421
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	728,308	841,715
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	728,308	841,715
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	610,877	626,255
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	610,877	626,255
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	108,959	105,096
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	108,959	105,096
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	449,560	741,369
Fair Value, Measurements, Recurring | Common stock | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	449,560	741,369
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	41,826	42,603
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	41,826	42,603
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	96,955	95,203
Fair Value, Measurements, Recurring | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	1,664	1,655
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	1,664	1,655
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	206,458	282,141
Fair Value, Measurements, Recurring | Money market instruments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	206,458	282,141
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	21	21
Fair Value, Measurements, Recurring | Other | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	21	21
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	387	213
Fair Value, Measurements, Recurring | Options sold | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Options sold	387	213
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