Segment Information - Information by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Gross written premiums	$ 31,247	$ 29,581	$ 26,981	$ 26,474	$ 31,308	$ 28,497	$ 29,725	$ 25,393
Net written premiums	27,439	18,395	23,082	22,324	27,069	24,634	26,176	22,050	$ 91,240	$ 99,929	$ 79,674
Net earned premiums	25,433	17,659	24,497	24,140	24,463	23,380	21,675	20,109	91,729	89,627	66,765
Other income	357	477	372	354	287	303	283	245	1,560	1,118	1,667
Total revenue									96,837	93,883	70,723
Losses and loss adjustment expenses, net	15,042	26,468	16,674	15,733	18,181	14,582	13,541	12,699	73,917	59,003	38,882
Policy acquisition costs	6,690	6,655	6,428	6,472	6,997	6,266	6,014	6,003	26,245	25,280	16,183
Operating expenses	3,993	4,474	4,370	4,530	4,211	4,710	4,536	4,139	17,367	17,596	14,806
Total expenses									118,891	102,526	70,640
Investment income	720	768	663	577	548	560	528	537	2,728	2,173	1,902
Net realized investment gains	39	39	0	(8)	761	71	541	(8)	70	1,365	285
Other gains (losses)	0	0	750	0	(400)	0	0	0	750	(400)	104
Interest expense	(616)	$ (303)	$ (219)	$ (224)	(179)	$ (168)	$ (143)	$ (157)	(1,362)	(647)	(769)
Income (loss) before income taxes									(22,054)	(8,643)	83
Deferred policy acquisition costs	12,781				13,290				12,781	13,290	12,102	$ 5,679
Unearned premiums	57,672				58,126				57,672	58,126
Loss and loss adjustment expense reserves	87,896				54,651				87,896	54,651	35,422	$ 31,531
Operating Segments | Commercial Lines
Segment Reporting Information [Line Items]
Gross written premiums									92,112	88,242	68,197
Net written premiums									78,217	78,439	58,157
Net earned premiums									76,786	68,921	48,586
Other income									628	378	1,099
Total revenue									77,414	69,299	49,685
Losses and loss adjustment expenses, net									55,701	42,441	25,730
Policy acquisition costs									20,470	18,560	11,937
Operating expenses									11,339	6,767	4,983
Total expenses									87,510	67,768	42,650
Segment underwriting gain (loss)									(10,096)	1,531	7,035
Deferred policy acquisition costs	10,116				10,156				10,116	10,156	8,401
Unearned premiums	45,951				44,484				45,951	44,484	33,337
Loss and loss adjustment expense reserves	76,586				46,917				76,586	46,917	29,739
Operating Segments | Personal Lines
Segment Reporting Information [Line Items]
Gross written premiums									22,172	26,681	25,553
Net written premiums									13,023	21,490	21,517
Net earned premiums									14,943	20,706	18,179
Other income									780	558	489
Total revenue									15,723	21,264	18,668
Losses and loss adjustment expenses, net									18,216	16,562	13,152
Policy acquisition costs									5,775	6,720	4,246
Operating expenses									2,570	2,911	3,305
Total expenses									26,561	26,193	20,703
Segment underwriting gain (loss)									(10,838)	(4,929)	(2,035)
Deferred policy acquisition costs	2,665				3,134				2,665	3,134	3,701
Unearned premiums	11,721				13,642				11,721	13,642	14,579
Loss and loss adjustment expense reserves	11,310				7,734				11,310	7,734	5,683
Corporate & Other
Segment Reporting Information [Line Items]
Gross written premiums									0	0	0
Net written premiums									0	0	0
Net earned premiums									0	0	0
Other income									152	182	79
Total revenue									152	182	79
Losses and loss adjustment expenses, net									0	0	0
Policy acquisition costs									0	0	0
Operating expenses									3,458	7,918	6,518
Total expenses									3,458	7,918	6,518
Segment underwriting gain (loss)									(3,306)	(7,736)	(6,439)
Investment income									2,728	2,173	1,902
Net realized investment gains									70	1,365	285
Other gains (losses)									750	(400)	104
Interest expense									(1,362)	(647)	(769)
Income (loss) before income taxes									(1,120)	(5,245)	(4,917)
Deferred policy acquisition costs	0				0				0	0	0
Unearned premiums	0				0				0	0	0
Loss and loss adjustment expense reserves	0				0				0	0	0
Operating Segments and Corporate Non Segment
Segment Reporting Information [Line Items]
Gross written premiums									114,284	114,923	93,750
Net written premiums									91,240	99,929	79,674
Net earned premiums									91,729	89,627	66,765
Other income									1,560	1,118	1,667
Total revenue									93,289	90,745	68,432
Losses and loss adjustment expenses, net									73,917	59,003	38,882
Policy acquisition costs									26,245	25,280	16,183
Operating expenses									17,367	17,596	14,806
Total expenses									117,529	101,879	69,871
Segment underwriting gain (loss)									(24,240)	(11,134)	(1,439)
Deferred policy acquisition costs	12,781				13,290				12,781	13,290	12,102
Unearned premiums	57,672				58,126				57,672	58,126	47,916
Loss and loss adjustment expense reserves	$ 87,896				$ 54,651				$ 87,896	$ 54,651	$ 35,422