Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	$ 3,959,679	$ 4,031,523
Equity securities:	946,015	970,939
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	3,959,679	4,031,523
Equity securities:	946,015	970,939
Short-term investments:	133,920	140,127
Assets, fair value disclosure	5,039,614	5,142,589
Liabilities	569	301
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	13,477	13,085
Equity securities:	779,229	797,024
Short-term investments:	115,043	124,379
Assets, fair value disclosure	907,749	934,488
Liabilities	569	301
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	3,946,202	4,018,438
Equity securities:	62,247	65,501
Short-term investments:	18,877	15,748
Assets, fair value disclosure	4,027,326	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:	13,477	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:	13,477	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:	2,780,244	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:	2,780,244	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:	151,840	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:	151,840	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:	511,952	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:	511,952	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:	314,193	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:	314,193	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:	187,973	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:	187,973	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:	779,229	797,024
Fair Value, Measurements, Recurring | Common stock | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities:	779,229	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:	62,247	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:	62,247	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:	104,539	108,414
Fair Value, Measurements, Recurring | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	20,324	17,201
Fair Value, Measurements, Recurring | Short-term bonds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	1,447	1,453
Fair Value, Measurements, Recurring | Short-term bonds | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	18,877	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:	113,570	122,917
Fair Value, Measurements, Recurring | Money market instruments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	113,570	122,917
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:	26	9
Fair Value, Measurements, Recurring | Other | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	26	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	569	301
Fair Value, Measurements, Recurring | Options sold | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liability	569	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