Investments, Securities with Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	$ 49,633	$ 53,282
12 months or longer	125,778	45,404
Total	175,411	98,686
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	1,592	816
12 months or longer	10,259	3,105
Total	11,851	3,921
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	0	12,175
12 months or longer	24,786	12,737
Total	24,786	24,912
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	0	162
12 months or longer	1,061	349
Total	1,061	511
Obligations of States and Political Subdivisions [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	0	999
12 months or longer	3,980	0
Total	3,980	999
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	0	1
12 months or longer	72	0
Total	72	1
Corporate Securities [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	49,633	40,108
12 months or longer	97,012	32,667
Total	146,645	72,775
Available-for-sale securities, continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 months	1,592	653
12 months or longer	9,126	2,756
Total	$ 10,718	$ 3,409