Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	$ 5,154,481	$ 4,913,378
Equity securities	746,227	879,175
Note receivable	10,024	31,231
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	5,154,481	4,913,378
Equity securities	746,227	879,175
Short-term investments	472,897	283,817
Note receivable	10,024	31,231
Assets, fair value disclosure	6,383,629	6,107,601
Total liabilities at fair value	599	213
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	63,740	75,874
Equity securities	606,000	741,369
Short-term investments	463,897	282,162
Note receivable	0	0
Assets, fair value disclosure	1,133,637	1,099,405
Total liabilities at fair value	599	213
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	5,090,741	4,837,504
Equity securities	42,132	42,603
Short-term investments	9,000	1,655
Note receivable	10,024	31,231
Assets, fair value disclosure	5,151,897	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
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 and agencies
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total fixed maturity securities	63,740	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	63,740	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	0	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	3,286,050	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	3,286,050	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	281,892	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	281,892	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	745,498	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	745,498	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	671,664	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	671,664	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	105,637	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	105,637	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	606,000	741,369
Fair Value, Measurements, Recurring | Common stock | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	606,000	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	42,132	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	42,132	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	98,095	95,203
Fair Value, Measurements, Recurring | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	9,000	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	9,000	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	463,878	282,141
Fair Value, Measurements, Recurring | Money market instruments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	463,878	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	19	21
Fair Value, Measurements, Recurring | Other | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	19	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	599	213
Fair Value, Measurements, Recurring | Options sold | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Options sold	599	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