Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	$ 4,489,552	$ 4,319,336
Equity securities	801,108	730,693
Note receivable	9,818	9,974
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	4,489,552	4,319,336
Equity securities	801,108	730,693
Short-term investments	162,466	178,491
Note receivable	9,818	9,974
Assets, fair value disclosure	5,462,944	5,238,494
Options sold	1,928	1,955
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	141,161	123,182
Equity securities	672,106	597,888
Short-term investments	160,636	176,653
Note receivable	0	0
Assets, fair value disclosure	973,903	897,723
Options sold	1,928	1,955
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	4,348,391	4,196,154
Equity securities	45,241	51,563
Short-term investments	1,830	1,838
Note receivable	9,818	9,974
Assets, fair value disclosure	4,405,280	4,259,529
Options sold	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
Note receivable	0	0
Assets, fair value disclosure	0	0
Options sold	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:	200,344	174,450
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:	141,161	123,182
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:	59,183	51,268
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:	2,795,677	2,777,258
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:	2,795,677	2,777,258
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:	193,040	186,887
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:	193,040	186,887
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:	706,210	599,630
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:	706,210	599,630
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:	495,523	484,947
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:	495,523	484,947
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:	98,758	96,164
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:	98,758	96,164
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	672,106	597,888
Fair Value, Measurements, Recurring | Common stock | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	672,106	597,888
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	45,241	51,563
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	45,241	51,563
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	83,761	81,242
Fair Value, Measurements, Recurring | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	13,970	13,853
Fair Value, Measurements, Recurring | Short-term bonds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	12,140	12,015
Fair Value, Measurements, Recurring | Short-term bonds | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	1,830	1,838
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	148,449	164,595
Fair Value, Measurements, Recurring | Money market instruments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	148,449	164,595
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	47	43
Fair Value, Measurements, Recurring | Other | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	47	43
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	1,928	1,955
Fair Value, Measurements, Recurring | Options sold | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Options sold	1,928	1,955
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