Investments, Securities with Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	$ 9,142	$ 49,633
12 months or longer	115,727	125,778
Total	124,869	175,411
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	135	1,592
12 months or longer	5,509	10,259
Total	5,644	11,851
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	0
12 months or longer	20,998	24,786
Total	20,998	24,786
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	0	0
12 months or longer	723	1,061
Total	723	1,061
Obligations of States and Political Subdivisions [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	0	0
12 months or longer	485	3,980
Total	485	3,980
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	0	0
12 months or longer	1	72
Total	1	72
Corporate Securities [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	9,142	49,633
12 months or longer	94,244	97,012
Total	103,386	146,645
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	135	1,592
12 months or longer	4,785	9,126
Total	$ 4,920	$ 10,718