Investments (Schedule of Unrealized Appreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Investments [Abstract]
Net change in unrealized appreciation on available-for-sale securities before deferred tax	$ 1,402	$ 343
Deferred income tax	(476)	(117)
Net change in unrealized appreciation on available-for-sale securities	$ 926	$ 226