Effects of Reinsurance on Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Insurance [Abstract]
Net Direct Unpaid Losses and LAE	$ 441,355	$ 138,345	$ 72,373
Net Assumed Unpaid Losses and LAE	40,877	2,510	4,419
Unpaid losses and loss adjustment expenses	482,232	140,855	76,792	$ 54,436
Net Ceded Unpaid Losses and LAE	(305,673)	(18,724)	(2,114)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	176,559	122,131	74,678
Direct Unearned Premiums, Net	528,419	371,149	287,148
Assumed Unearned Premiums, Net	27,454	1,074	17,506
Unearned Premiums, Gross	555,873	372,223	304,654
Ceded Unearned Premiums, Net	(201,904)	(132,564)	(79,400)
Unearned Premiums, Net	$ 353,969	$ 239,659	$ 225,254