Quarterly Results of Operations (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Results of Operations (Unaudited) [Abstract]
Net premiums earned	$ 68,933	$ 65,947	$ 62,905	$ 63,842	$ 65,422	$ 64,448	$ 61,775	$ 61,098	$ 261,627	$ 252,743	$ 237,461
Net investment income	2,599	2,073	2,090	2,294	2,183	2,192	1,985	2,410	9,055	8,770	9,930
Net gains on investments	2,113	658	8,089	4,070	7,019	1,430	719	14,347
Losses and loss expenses incurred	41,332	38,693	40,282	39,289	40,858	36,967	38,343	34,533	159,596	150,701	138,088
Net income	$ 8,246	$ 5,770	$ 9,340	$ 6,361	$ 8,967	$ 7,771	$ 4,907	$ 14,943	$ 29,717	$ 36,588	$ 31,919
Net income per share - diluted (in dollars per share)	$ 0.55	$ 0.39	$ 0.62	$ 0.42	$ 0.60	$ 0.52	$ 0.33	$ 1.00