Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Premiums Written, Net [Abstract]
Direct written premiums	$ 69,546	$ 55,633	$ 203,374	$ 166,248
Ceded written premiums	(11,602)	(8,562)	(29,448)	(25,242)
Net written premiums	57,944	47,071	173,926	141,006
Premiums Earned, Net [Abstract]
Direct earned premiums	64,713	53,527	180,909	153,293
Ceded earned premiums	(10,417)	(8,497)	(27,659)	(24,778)
Net earned premiums	54,296	45,030	153,250	128,515
Ceded incurred losses and loss adjustment expenses	15,100	$ 6,900	23,000	$ 8,700
Reinsurance recoverables on paid losses	1,400		1,400		$ 1,400
Reinsurance recoverables on unpaid losses	$ 63,500		$ 63,500		$ 48,200