Condensed Financial Information of Registrant (Schedule Of Condensed Financial Information Of Registrant, Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments, at fair value:
Equity securities (cost $69,371; $75,099)	$ 970,939	$ 803,851
Short-term investments (cost $20,441; $4,269)	140,127	375,609
Total investments	5,142,589	4,729,270
Cash	335,557	348,479
Accrued investment income	43,299	42,985
Current income taxes	20,108	0
Other assets	27,970	38,635
Total assets	6,772,472	6,328,246
Liabilities
Notes payable	372,931	372,532
Deferred income taxes	53,569	41,132
Other liabilities	255,760	236,136
Total liabilities	4,632,191	4,295,649
Shareholders’ equity:
Common stock	98,943	98,970
Retained earnings	2,041,338	1,933,627
Total shareholders’ equity	2,140,281	2,032,597	$ 1,799,502
Total liabilities and shareholders’ equity	6,772,472	6,328,246
Cost - equity security trading investments	754,536	695,150
Cost - short-term investments	141,206	376,547
Parent Company
Investments, at fair value:
Equity securities (cost $69,371; $75,099)	111,399	110,596
Short-term investments (cost $20,441; $4,269)	20,441	4,269
Investment in subsidiaries	2,332,717	2,285,417
Total investments	2,464,557	2,400,282
Cash	53,738	24,652
Accrued investment income	16	20
Amounts receivable from affiliates	457	250
Current income taxes	20,738	0
Income tax receivable from affiliates	14,202	5,862
Other assets	771	221
Total assets	2,554,479	2,431,287
Liabilities
Notes payable	372,931	372,532
Amounts payable to affiliates	0	30
Income tax payable to affiliates	25,626	2,724
Current income taxes	0	10,074
Deferred income taxes	10,811	8,470
Other liabilities	4,830	4,860
Total liabilities	414,198	398,690
Shareholders’ equity:
Common stock	98,943	98,970
Retained earnings	2,041,338	1,933,627
Total shareholders’ equity	2,140,281	2,032,597
Total liabilities and shareholders’ equity	2,554,479	2,431,287
Cost - equity security trading investments	69,371	75,099
Cost - short-term investments	$ 20,441	$ 4,269