Reinsurance (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Effect of reinsurance transactions on our premium, loss and loss adjustment expense and policy acquisition costs
Direct written premium	$ 713,110	$ 677,996	$ 1,294,681	$ 1,222,766
Reinsurance assumed	96,333	113,557	234,967	251,476
Reinsurance ceded	(180,409)	(149,465)	(321,430)	(273,750)
Net written premium	629,034	642,088	1,208,218	1,200,492
Direct earned premium	621,224	602,354	1,237,629	1,193,537
Reinsurance assumed	86,036	86,544	171,308	168,882
Reinsurance ceded	(145,904)	(123,567)	(286,395)	(249,947)
Net earned premium	561,356	565,331	1,122,542	1,112,472
Direct loss and loss adjustment expense	335,968	362,529	693,480	727,921
Reinsurance assumed	71,017	24,326	110,708	61,035
Reinsurance ceded	(67,511)	(50,030)	(132,017)	(123,203)
Net loss and loss adjustment expense	339,474	336,825	672,171	665,753
Policy acquisition costs	103,745	102,421	204,031	198,156
Ceding commissions	(32,949)	(27,931)	(66,286)	(54,222)
Net policy acquisition costs	$ 70,796	$ 74,490	$ 137,745	$ 143,934