Condensed Financial Information of Registrant (Schedule Of Condensed Financial Information Of Registrant, Statements Of Cash Flow) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net cash provided by (used in) operating activities	$ 287,473	$ 190,244	$ 246,535
Equity securities available for sale in nature
Purchases	(1,077,638)	(965,701)	(542,494)
Sales	696,138	805,417	745,058
(Decrease) in payable for securities, net	29,958	(1,387)	9,294
Business acquisition, net of cash acquired	0	7,771	0
Other, net	3,605	2,473	3,472
Net cash used in investing activities	(226,720)	(81,682)	(194,035)
Cash flows from financing activities:
Dividends paid to shareholders	(137,201)	(136,386)	(135,496)
Excess tax benefits related to share-based compensation	913	27	148
Proceeds from stock options exercised	1,632	2,111	6,247
Proceeds from bank loan	30,000	0	100,000
Net cash used in financing activities	(104,656)	(134,248)	(29,101)
Net increase (decrease) in cash	(43,903)	(25,686)	23,399
Cash:
Beginning of year	264,221	289,907	266,508
End of year	220,318	264,221	289,907
SUPPLEMENTAL CASH FLOW DISCLOSURE
Interest paid	3,531	2,989	2,543
Income taxes (refunded)	(183)
Income taxes paid		31,390	61,139
Parent Company [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	526	548	(3,434)
Cash flows from investing activities:
Capital contribution to subsidiaries	(30,125)	(90,125)	(30,125)
Distributions received from special purpose entities	4,898	8,883	6,756
Dividends received from subsidiaries	110,800	133,000	225,000
Purchases of fixed maturity securities available for sale in nature	(1,060)	(571)	0
Equity securities available for sale in nature
Purchases	(64,807)	(146,236)	(254,572)
Sales	73,942	192,005	90,422
(Decrease) in payable for securities, net	0	0	(2,489)
Net decrease in short-term investments	(515)	(8,612)	(1,346)
Business acquisition, net of cash acquired	0	(6,000)
Other, net	1,614	1,945	2,191
Net cash used in investing activities	95,777	101,513	38,529
Cash flows from financing activities:
Dividends paid to shareholders	(137,201)	(136,386)	(135,496)
Excess tax benefits related to share-based compensation	913	27	148
Proceeds from stock options exercised	1,632	2,111	6,247
Proceeds from bank loan	30,000	0	100,000
Net cash used in financing activities	(104,656)	(134,248)	(29,101)
Net increase (decrease) in cash	(8,353)	(32,187)	5,994
Cash:
Beginning of year	20,139	52,326	46,332
End of year	11,786	20,139	52,326
SUPPLEMENTAL CASH FLOW DISCLOSURE
Interest paid	2,397	2,153	1,757
Income taxes (refunded)	$ (339)
Income taxes paid		$ 1,807	$ 2,112