Investments (Credit Quality of Agricultural and Residential Mortgage Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Agricultural Mortgage Loans - by Credit Quality Indicator:
Recorded Investment	$ 127,610	$ 121,858
% of Total	100.00%	100.00%
Less than 65%
Agricultural Mortgage Loans - by Credit Quality Indicator:
Recorded Investment	$ 125,752	$ 119,974
% of Total	98.50%	98.40%
65% to 75%
Agricultural Mortgage Loans - by Credit Quality Indicator:
Recorded Investment	$ 1,858	$ 1,884
% of Total	1.50%	1.60%