Reinsurance (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
Effect of reinsurance transactions on our premium, loss and loss adjustment expense and policy acquisition costs
Direct written premium	$ 603,844	$ 555,427	$ 1,826,610	$ 1,724,869
Reinsurance assumed	61,919	73,420	313,395	295,268
Reinsurance ceded	(135,456)	(116,513)	(409,206)	(359,046)
Net written premium	530,307	512,334	1,730,799	1,661,091
Direct earned premium	601,572	574,571	1,795,109	1,728,082
Reinsurance assumed	90,988	96,799	259,870	255,293
Reinsurance ceded	(128,910)	(127,114)	(378,857)	(406,388)
Net earned premium	563,650	544,256	1,676,122	1,576,987
Direct loss and loss adjustment expense	301,306	410,573	1,029,227	1,197,225
Reinsurance assumed	35,108	44,600	96,143	186,805
Reinsurance ceded	(32,400)	(74,801)	(155,603)	(321,790)
Net loss and loss adjustment expense	304,014	380,372	969,767	1,062,240
Policy acquisition costs	101,698	100,975	299,854	292,645
Ceding commissions	(34,078)	(43,479)	(88,300)	(99,465)
Net policy acquisition costs	$ 67,620	$ 57,496	$ 211,554	$ 193,180