Reinsurance (Reinsurance Transactions Effect) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Effect of reinsurance transactions on our premium, loss and loss adjustment expense and policy acquisition costs
Direct written premium	$ 900,536	$ 749,239	$ 1,617,584	$ 1,369,751
Reinsurance assumed	77,217	83,490	186,305	209,700
Reinsurance ceded	(211,620)	(185,715)	(368,840)	(342,255)
Net written premium	766,133	647,014	1,435,049	1,237,196
Direct earned premium	742,135	651,682	1,445,719	1,288,995
Reinsurance assumed	72,833	76,318	144,001	152,341
Reinsurance ceded	(173,128)	(155,752)	(347,317)	(306,476)
Net earned premium	641,840	572,248	1,242,403	1,134,860
Direct loss and loss adjustment expense	478,656	383,987	937,382	743,616
Reinsurance assumed	11,714	21,472	38,930	63,274
Reinsurance ceded	(95,065)	(69,562)	(215,845)	(140,247)
Net loss and loss adjustment expense	395,305	335,897	760,467	666,643
Policy acquisition costs	123,925	110,565	238,995	215,210
Ceding commissions	(45,466)	(37,595)	(85,325)	(73,199)
Net policy acquisition costs	$ 78,459	$ 72,970	$ 153,670	$ 142,011