Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of period	$ 14,123	$ 11,578	$ 11,775	$ 10,150
Policy acquisition costs deferred:
Direct commissions deferred	10,232	8,024	29,907	24,529
Ceding commissions deferred	(3,123)	(2,519)	(8,273)	(7,502)
Other underwriting and policy acquisition costs	781	713	2,284	2,230
Policy acquisition costs deferred	7,890	6,218	23,918	19,257
Amortization of net policy acquisition costs	(7,528)	(6,071)	(21,208)	(17,682)
Balance, end of period	$ 14,485	$ 11,725	$ 14,485	$ 11,725