Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Results of Operations (Unaudited) [Abstract]
Net premiums earned	$ 111,357	$ 110,288	$ 115,631	$ 110,012	$ 118,671	$ 96,807	$ 111,940	$ 105,462	$ 447,288	$ 432,880	$ 328,145
Net investment income	6,815	6,703	6,500	6,231	6,038	5,578	5,796	4,636	26,249	22,048	18,095
Net realized and unrealized gains (losses) on investments	3,848	125	2,889	6,027	(20,096)	2,373	(3,435)	(4,533)	12,889	(25,691)	19,686
Losses and loss expenses incurred	86,132	84,781	90,433	87,122	101,537	94,540	77,488	72,298	348,468	345,864	247,518
Net income (loss)	$ 3,771	$ (707)	$ 1,535	$ 2,748	$ (24,567)	$ (12,325)	$ 2,487	$ 330	$ 7,347	$ (34,075)	$ 18,323
Net income (loss) per share (in dollars per share)	$ 0.26	$ (0.05)	$ 0.11	$ 0.18	$ (1.65)	$ (0.82)	$ 0.17	$ 0.02	$ 0.50	$ (2.28)	$ 1.21