Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Allowance for Uncollectible Premium	$ 384	$ 144
Finite-Lived Intangible Asset, Useful Life	7 years
Advertising Expense	$ 1,013	907	$ 2,630
Concentration Risk, Percentage	52.00%
Cash, FDIC Insured Amount	$ 314,147	$ 159,288
Cash, FDIC Insured Amount, Period Increase (Decrease)	$ 154,859