Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	$ 12,768	$ 10,501	$ 11,775	$ 10,150
Policy acquisition costs deferred:
Direct commissions deferred	10,298	8,625	19,675	16,505
Ceding commissions deferred	(2,609)	(2,392)	(5,150)	(4,983)
Other underwriting and policy acquisition costs	694	756	1,503	1,517
Policy acquisition costs deferred	8,383	6,989	16,028	13,039
Amortization of net policy acquisition costs	(7,028)	(5,912)	(13,680)	(11,611)
Balance, end of period	$ 14,123	$ 11,578	$ 14,123	$ 11,578