Condensed Financial Information of Registrant (Schedule Of Condensed Financial Information Of Registrant, Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investments, at fair value:
Equity securities	$ 281,883	$ 477,088
Short-term investments	315,776	294,653
Total investments	3,158,312	3,180,095
Cash	266,508	158,183		211,393	181,388
Accrued investment income	36,120	31,109
Current income taxes	0	7,058
Deferred income taxes	15,220	0
Other assets	14,336	11,863
Total assets	4,315,181	4,189,686
LIABILITIES AND SHAREHOLDERS’ EQUITY
Notes payable	190,000	140,000
Accounts payable and accrued expenses	127,663	96,220
Current income taxes	11,856	0
Deferred income taxes	0	445
Other liabilities	170,665	153,972
Total liabilities	2,492,695	2,347,189
Shareholders’ equity:
Common stock	81,591	79,380
Additional paid -in capital	411	0
Retained earnings	1,740,484	1,763,117
Total shareholders’ equity	1,822,486	1,842,497	1,857,483
Total liabilities and shareholders’ equity	4,315,181	4,189,686
Parent Company [Member]
Investments, at fair value:
Equity securities	29,737	27,127
Short-term investments	11,089	47,174
Investment in subsidiaries	1,794,164	1,760,760
Total investments	1,834,990	1,835,061
Cash	46,332	10,199	29,219	41,606
Accrued investment income	16	4
Amounts receivable from affiliates	206	200
Current income taxes	0	6,333
Deferred income taxes	1,068	729
Income tax receivable from affiliates	11,573	6,182
Other assets	459	0
Total assets	1,894,644	1,858,708
LIABILITIES AND SHAREHOLDERS’ EQUITY
Notes payable	50,000	0
Accounts payable and accrued expenses	23	47
Amounts payable to affiliates	34	95
Income tax payable to affiliates	6,730	16,069
Current income taxes	12,672	0
Other liabilities	2,699	0
Total liabilities	72,158	16,211
Shareholders’ equity:
Common stock	81,591	79,380
Additional paid -in capital	411	0
Retained earnings	1,740,484	1,763,117
Total shareholders’ equity	1,822,486	1,842,497
Total liabilities and shareholders’ equity	1,894,644	1,858,708
Equity securities trading - cost	27,499	31,178
Short-term investments - cost	$ 11,089	$ 47,174