Investments (Allowance for Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	$ 2,651	$ 4,154
Addition to (release of) allowance for losses	(1,093)	(1,503)
Charge-offs, net of recoveries	0	0
Allowance for credit losses, total ending balance	1,558	2,651
Commercial mortgage and other loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	2,587	4,071
Addition to (release of) allowance for losses	(1,074)	(1,484)
Charge-offs, net of recoveries	0	0
Allowance for credit losses, total ending balance	1,513	2,587
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	64	83
Addition to (release of) allowance for losses	(19)	(19)
Charge-offs, net of recoveries	0	0
Allowance for credit losses, total ending balance	45	64
Uncollateralized loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	0	0
Addition to (release of) allowance for losses	0	0
Charge-offs, net of recoveries	0	0
Allowance for credit losses, total ending balance	$ 0	$ 0