Reinsurance (Effect Of Reinsurance On Premiums Written And Earned) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Reinsurance Disclosures [Abstract]
Direct premiums written	$ 518,540	$ 473,210
Direct premiums earned	509,589	446,138
Assumed premiums written	130,078	117,573
Assumed premiums earned	83,842	81,450
Ceded premiums written	(67,452)	(71,771)
Ceded premiums earned	(63,835)	(64,477)
Net premiums written	581,166	519,012
Net premiums earned	$ 529,596	$ 463,111