Reinsurance (Effect Of Reinsurance On Premiums Written And Earned) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Reinsurance Disclosures [Abstract]
Direct premiums written	$ 519,408	$ 501,687	$ 1,568,092	$ 1,482,903
Direct premiums earned	505,514	475,578	1,505,710	1,383,678
Assumed premiums written	91,425	82,948	338,281	289,708
Assumed premiums earned	94,822	86,134	269,771	254,907
Ceded premiums written	(71,209)	(59,957)	(218,969)	(198,233)
Ceded premiums earned	(69,799)	(52,509)	(202,292)	(176,070)
Net premiums written	539,624	524,678	1,687,404	1,574,378
Net premiums earned	$ 530,537	$ 509,203	$ 1,573,189	$ 1,462,515