Investments, Securities with Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	$ 53,282	$ 91,645
12 months or longer	45,404	20,587
Total Fair Value	98,686	112,232
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	816	2,985
12 months or longer	3,105	2,556
Total Unrealized Losses	3,921	5,541
Fixed Maturities - U.S. Treasury Securities and Obligations of U.S. Government Agencies and Authorities [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	12,175	23,494
12 months or longer	12,737	0
Total Fair Value	24,912	23,494
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	162	553
12 months or longer	349	0
Total Unrealized Losses	511	553
Fixed Maturities - Obligations of States and Political Subdivisions [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	999	8,747
12 months or longer	0	0
Total Fair Value	999	8,747
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	1	308
12 months or longer	0	0
Total Unrealized Losses	1	308
Fixed Maturities - Corporate Securities [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	40,108	59,404
12 months or longer	32,667	20,587
Total Fair Value	72,775	79,991
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	653	2,124
12 months or longer	2,756	2,556
Total Unrealized Losses	$ 3,409	$ 4,680