General (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Potentially dilutive securities (in shares)	85,000	0	71,000	0
Deferred policy acquisition cost amortization	$ 141,520	$ 137,839	$ 282,504	$ 280,438
Advertising expenses			23,000	20,000
Revenue from contract with customer			8,300	7,700	$ 15,200
Contract with customer, related expenses			$ 5,400	$ 5,300	$ 10,200
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, percentage of revenue			0.50%	0.50%	0.40%
Commission income receivable	1,100		$ 1,100		$ 1,200
Refund liability	$ 700		$ 700		$ 700
Auto Insurance Specialists LLC and Poliseek AIS Insurance Solutions Inc
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, percentage of revenue			80.00%