Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Results of Operations (Unaudited) [Abstract]
Net premiums earned	$ 69,141	$ 71,235	$ 68,726	$ 66,909	$ 65,995	$ 65,445	$ 65,449	$ 66,446	$ 276,011	$ 263,335	$ 261,627
Net investment income	3,982	3,513	3,549	3,440	3,771	3,014	2,898	2,815	14,483	12,498	9,055
Net gains (losses) on investments	6,204	7,732	280	9,012	(1,753)	(2,086)	(1,166)	3,743
Losses and loss expenses incurred	48,366	56,827	42,666	38,623	41,860	35,212	37,031	41,646	186,481	155,750	159,596
Net income	$ 4,864	$ 4,001	$ 5,969	$ 14,112	$ 3,541	$ 7,780	$ 5,718	$ 6,243	$ 28,945	$ 23,283	$ 29,717
Net income per share - diluted (in dollars per share)	$ 0.32	$ 0.27	$ 0.40	$ 0.94	$ 0.24	$ 0.52	$ 0.38	$ 0.42