Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	$ 3,878,684	$ 4,031,523
Equity securities:	782,802	970,939
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	3,878,684	4,031,523
Equity securities:	782,802	970,939
Short-term investments:	172,130	140,127
Assets, fair value disclosure	4,833,616	5,142,589
Liabilities	122	301
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	14,026	13,085
Equity securities:	635,185	797,024
Short-term investments:	157,466	124,379
Assets, fair value disclosure	806,677	934,488
Liabilities	122	301
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities:	3,864,658	4,018,438
Equity securities:	57,721	65,501
Short-term investments:	14,664	15,748
Assets, fair value disclosure	3,937,043	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:	14,026	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:	14,026	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:	2,710,968	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:	2,710,968	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:	156,074	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:	156,074	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:	522,529	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:	522,529	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:	301,046	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:	301,046	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:	174,041	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:	174,041	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:	635,185	797,024
Fair Value, Measurements, Recurring | Common stock | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities:	635,185	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:	57,721	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:	57,721	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:	89,896	108,414
Fair Value, Measurements, Recurring | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	11,979	17,201
Fair Value, Measurements, Recurring | Short-term bonds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	795	1,453
Fair Value, Measurements, Recurring | Short-term bonds | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	11,184	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:	160,123	122,917
Fair Value, Measurements, Recurring | Money market instruments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	156,643	122,917
Fair Value, Measurements, Recurring | Money market instruments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	3,480	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:	28	9
Fair Value, Measurements, Recurring | Other | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments:	28	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	122	301
Fair Value, Measurements, Recurring | Options sold | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liability	122	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