Investments (Credit Quality of Commercial Mortgage Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	$ 281,552	$ 286,002
% of Total	100.00%	100.00%
Less than 65%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	$ 271,887	$ 276,324
% of Total	96.60%	96.60%
65% to 75%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	$ 9,665	$ 9,678
% of Total	3.40%	3.40%
Greater than 1.20x
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	$ 265,122	$ 269,389
Greater than 1.20x | Less than 65%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	255,457	259,711
Greater than 1.20x | 65% to 75%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	9,665	9,678
1.00x - 1.20x
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	15,431	15,614
1.00x - 1.20x | Less than 65%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	15,431	15,614
1.00x - 1.20x | 65% to 75%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	0	0
Less than 1.00x
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	999	999
Less than 1.00x | Less than 65%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	999	999
Less than 1.00x | 65% to 75%
Mortgage Loans on Real Estate [Line Items]
Commercial mortgage loans	$ 0	$ 0