Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	$ 14,801	$ 11,775
Policy acquisition costs deferred:
Direct commissions deferred	12,363	9,377
Ceding commissions deferred	(3,256)	(2,541)
Other underwriting and policy acquisition costs	965	809
Policy acquisition costs deferred	10,072	7,645
Amortization of net policy acquisition costs	(8,559)	(6,652)
Balance, end of period	$ 16,314	$ 12,768