Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	$ 11,775	$ 10,150
Policy acquisition costs deferred:
Direct commissions deferred	9,377	7,880
Ceding commissions deferred	(2,541)	(2,591)
Other underwriting and policy acquisition costs	809	761
Policy acquisition costs deferred	7,645	6,050
Amortization of net policy acquisition costs	(6,652)	(5,699)
Balance, end of period	$ 12,768	$ 10,501