Condensed Financial Information of Registrant (Schedule Of Condensed Financial Information Of Registrant, Statements Of Cash Flow) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net cash provided by operating activities	$ 519,678,000	$ 383,434,000	$ 341,405,000
Cash flows from investing activities:
Capital distribution from subsidiaries	5,200,000	6,000,000.0
Fixed maturity securities available for sale in nature:
Sales	136,560,000	189,306,000	100,709,000
Equity securities available for sale in nature
Purchases	(1,174,759,000)	(1,026,827,000)	(831,310,000)
Sales	1,088,701,000	954,755,000	679,571,000
Other, net	6,247,000	10,105,000	1,934,000
Net cash used in investing activities	(401,201,000)	(222,436,000)	(185,597,000)
Cash flows from financing activities:
Dividends paid to shareholders	(139,071,000)	(138,478,000)	(137,886,000)
Proceeds from stock options exercised	701,000	358,000	2,162,000
Net proceeds from issuance of senior notes	0	0	371,011,000
Payoff of principal on loan and credit facilities	0	0	(320,000,000)
Net cash used in financing activities	(138,370,000)	(138,120,000)	(84,713,000)
Net (decrease) increase in cash	(19,893,000)	22,878,000	71,095,000
Cash:
Beginning of year	314,291,000	291,413,000	220,318,000
End of year	294,398,000	314,291,000	291,413,000
SUPPLEMENTAL CASH FLOW DISCLOSURE
Interest paid	16,586,000	16,586,000	9,863,000
Income taxes (refunded) paid, net	(14,564,000)	(10,989,000)	25,218,000
Parent Company [Member]
Cash flows from operating activities:
Net cash provided by operating activities	(5,392,000)	(16,108,000)	(14,503,000)
Cash flows from investing activities:
Capital contribution to subsidiaries	(125,000)	(540,619)	(140,125,000)
Capital distribution from subsidiaries	30,068,567	0	0
Distributions received from special purpose entities	5,153,000	5,998,000	5,243,000
Dividends received from subsidiaries	114,431,000	135,000,000	109,000,000
Fixed maturity securities available for sale in nature:
Sales	0	0	1,614,000
Equity securities available for sale in nature
Purchases	(39,966,000)	(22,286,000)	(22,406,000)
Sales	74,663,000	33,052,000	18,876,000
Calls	0	0	4,000,000
(Increase) decrease in short-term investments	(25,213,000)	18,065,000	(20,607,000)
Other, net	376,000	605,000	310,000
Net cash used in investing activities	159,388,000	169,893,000	(44,095,000)
Cash flows from financing activities:
Dividends paid to shareholders	(139,071,000)	(138,478,000)	(137,886,000)
Proceeds from stock options exercised	701,000	358,000	2,162,000
Net proceeds from issuance of senior notes	0	0	371,011,000
Payoff of principal on loan and credit facilities	0	0	(180,000,000)
Net cash used in financing activities	(138,370,000)	(138,120,000)	55,287,000
Net (decrease) increase in cash	15,626,000	15,665,000	(3,311,000)
Cash:
Beginning of year	24,140,000	8,475,000	11,786,000
End of year	39,766,000	24,140,000	8,475,000
SUPPLEMENTAL CASH FLOW DISCLOSURE
Interest paid	16,586,000	16,586,000	9,435,000
Income taxes (refunded) paid, net	$ (12,391,000)	$ 4,296,000	$ 346,000