Quarterly Results of Operations (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Results of Operations (Unaudited) [Abstract]
Net premiums earned	$ 61,402	$ 54,853	$ 59,655	$ 61,551	$ 64,196	$ 60,429	$ 62,344	$ 57,601	$ 237,461	$ 244,570	$ 214,738
Net investment income	2,734	2,343	2,431	2,422	2,652	2,779	2,644	2,653	9,930	10,729	11,335
Net gains (losses) on investments	302	8,781	(5,453)	5,381	3,088	(17,460)	(1,963)	(1,469)
Losses and loss expenses incurred	38,970	30,477	33,739	34,904	46,079	48,637	55,166	65,673	138,088	215,555	145,952
Net income (loss)	$ 4,676	$ 11,687	$ 4,050	$ 11,506	$ 5,498	$ (12,971)	$ (5,504)	$ (15,198)	$ 31,919	$ (28,175)	$ 25,015
Net income (loss) per share - diluted (in dollars per share)	$ 0.31	$ 0.78	$ 0.27	$ 0.78	$ 0.37	$ (0.87)	$ (0.38)	$ (1.02)