Investments, Net Investment Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest [Abstract]
Taxable bonds	$ 6,233	$ 6,031	$ 4,509
Municipal bonds (tax exempt)	3,619	1,808	1,514
Dividends on equity securities	1,041	442	372
Cash, cash equivalents, and short-term investments	678	93	9
Gross investment income	11,571	8,374	6,404
Investment expenses	(1,002)	(887)	(761)
Net investment income	$ 10,569	$ 7,487	$ 5,643