Liability for Unpaid Losses and Loss Adjustment Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Current Year Claims and Claims Adjustment Expense	$ 368,148	$ 281,365	$ 185,476
Prior Year Claims and Claims Adjustment Expense	(2,613)	16,988	(2,368)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	365,535	298,353	183,108
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	256,134	210,970	127,306
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	95,272	62,506	36,698
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	351,406	273,476	164,004
Liability for Unpaid Claims and Claims Adjustment Expense, Net	176,559	122,131	74,678
Reinsurance Recoverable on Unpaid Losses and LAE			2,114	$ 1,252
Liability for Unpaid Claims and Claims Adjustment Expense, Net, Including Acquisition		122,131	74,678	53,184
Unpaid losses and loss adjustment expenses	482,232	140,855	76,792	$ 54,436
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	236,253	83,447	45,502
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	$ 245,979	$ 57,408	$ 31,290