Fair Value Measurements (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	$ 4,031,523	$ 3,549,810
Equity securities	970,939	803,851
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	4,031,523	3,549,810
Equity securities	970,939	803,851
Short-term investments	140,127	375,609
Note receivable		5,725
Total assets at fair value	5,142,589	4,734,995
Liabilities fair value	301
Fair Value, Measurements, Recurring [Member] | U.S. government bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	13,085	13,816
Fair Value, Measurements, Recurring [Member] | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	2,843,221	2,791,212
Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	137,002	93,264
Fair Value, Measurements, Recurring [Member] | Corporate securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	523,853	241,366
Fair Value, Measurements, Recurring [Member] | Collateralized loan obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	314,153	256,891
Fair Value, Measurements, Recurring [Member] | Other asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	200,209	153,261
Fair Value, Measurements, Recurring [Member] | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	797,024	691,782
Fair Value, Measurements, Recurring [Member] | Non-redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	65,501	32,660
Fair Value, Measurements, Recurring [Member] | Private Equity Funds Net Asset Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	108,414	79,409
Fair Value, Measurements, Recurring [Member] | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	17,201	26,928
Fair Value, Measurements, Recurring [Member] | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	122,917	348,676
Fair Value, Measurements, Recurring [Member] | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	9	5
Fair Value, Measurements, Recurring [Member] | Options sold
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilitly	301
Fair Value, Measurements, Recurring [Member] | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	13,085	13,816
Equity securities	797,024	691,782
Short-term investments	124,379	370,680
Note receivable		0
Total assets at fair value	934,488	1,076,278
Liabilities fair value	301
Fair Value, Measurements, Recurring [Member] | Level 1 | U.S. government bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	13,085	13,816
Fair Value, Measurements, Recurring [Member] | Level 1 | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 | Mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 | Corporate securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 | Collateralized loan obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 | Other asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	797,024	691,782
Fair Value, Measurements, Recurring [Member] | Level 1 | Non-redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	1,453	21,999
Fair Value, Measurements, Recurring [Member] | Level 1 | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	122,917	348,676
Fair Value, Measurements, Recurring [Member] | Level 1 | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	9	5
Fair Value, Measurements, Recurring [Member] | Level 1 | Options sold
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilitly	301
Fair Value, Measurements, Recurring [Member] | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	4,018,438	3,535,994
Equity securities	65,501	32,660
Short-term investments	15,748	4,929
Note receivable		5,725
Total assets at fair value	4,099,687	3,579,308
Liabilities fair value	0
Fair Value, Measurements, Recurring [Member] | Level 2 | U.S. government bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	2,843,221	2,791,212
Fair Value, Measurements, Recurring [Member] | Level 2 | Mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	137,002	93,264
Fair Value, Measurements, Recurring [Member] | Level 2 | Corporate securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	523,853	241,366
Fair Value, Measurements, Recurring [Member] | Level 2 | Collateralized loan obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	314,153	256,891
Fair Value, Measurements, Recurring [Member] | Level 2 | Other asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	200,209	153,261
Fair Value, Measurements, Recurring [Member] | Level 2 | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 | Non-redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	65,501	32,660
Fair Value, Measurements, Recurring [Member] | Level 2 | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	15,748	4,929
Fair Value, Measurements, Recurring [Member] | Level 2 | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 | Options sold
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilitly	0
Fair Value, Measurements, Recurring [Member] | 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
Total assets at fair value	0	0
Liabilities fair value	0
Fair Value, Measurements, Recurring [Member] | Level 3 | U.S. government bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Municipal securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Corporate securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Collateralized loan obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Other asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Common stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Non-redeemable preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Short-term bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 | Other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	0	$ 0
Fair Value, Measurements, Recurring [Member] | Level 3 | Options sold
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilitly	$ 0