Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Premiums Written, Net [Abstract]
Direct written premiums	$ 69,981	$ 57,753	$ 133,828	$ 110,615
Assumed written premiums	0	0	0	0
Ceded written premiums	(9,090)	(7,980)	(17,846)	(16,680)
Net written premiums	60,891	49,773	115,982	93,935
Premiums Earned, Net [Abstract]
Direct earned premiums	59,603	51,304	116,196	99,766
Assumed earned premiums	0	0	0	0
Ceded earned premiums	(8,710)	(8,252)	(17,242)	(16,281)
Net earned premiums	50,893	43,052	98,954	83,485
Ceded incurred losses and loss adjustment expenses	5,000	$ (600)	7,900	$ 1,800
Reinsurance recoverables on paid losses	1,000		1,000		$ 1,400
Reinsurance recoverables on unpaid losses	$ 53,400		$ 53,400		$ 48,200