Reinsurance (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net written premiums:
Direct	$ 260,692	$ 241,180	$ 234,158
Assumed	58,552	57,365	43,404
Ceded	(63,884)	(57,927)	(54,322)
Net	255,360	240,618	223,240
Net earned premiums:
Direct	249,810	241,428	231,419
Assumed	60,756	51,047	40,872
Ceded earned premiums	(56,700)	(59,596)	(71,558)
Net earned premiums	253,866	232,879	200,733
Losses and loss adjustment expenses incurred:
Direct	200,218	152,592	136,140
Assumed	39,276	48,699	26,038
Ceded	(67,796)	(31,924)	(41,883)
Net	171,698	169,367	120,295
Unpaid loss and loss adjustment expenses:
Direct	597,238	570,835	568,740
Assumed	128,007	109,366	80,901
Ceded	(185,649)	(173,267)	(196,590)
Net	$ 539,596	$ 506,934	$ 453,051