Investments, Summary of Realized Investment Gains (Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Summary of realized investment gains (losses) [Abstract]
Gains	$ 9,310	$ 2,684
Losses	(142)	(89)
Realized investment gains, net	9,168	2,595
Proceeds from sales of investments [Abstract]
Total proceeds	$ 83,992	62,361
Percentage of investment grade securities in bond portfolio	92.00%
Fixed Maturities [Member]
Summary of realized investment gains (losses) [Abstract]
Gains	$ 2,226	1,119
Losses	(142)	(89)
Realized investment gains, net	2,084	1,030
Proceeds from sales of investments [Abstract]
Total proceeds	72,760	59,072
Equity Securities [Member]
Summary of realized investment gains (losses) [Abstract]
Gains	1,044	0
Losses	0	0
Realized investment gains, net	1,044	0
Proceeds from sales of investments [Abstract]
Total proceeds	1,579	0
Other Investments [Member]
Summary of realized investment gains (losses) [Abstract]
Gains	6,040	1,565
Losses	0	0
Realized investment gains, net	6,040	1,565
Proceeds from sales of investments [Abstract]
Total proceeds	$ 9,653	$ 3,289