Investments (Allowance for Losses) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	$ 2,289	$ 643
Allowance for Loan and Lease Losses, Adjustments, Other	(11)	1,646
Allowance for Loan and Lease Losses Write-offs, Net	0	0
Total ending balance	2,278	2,289
Commercial Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	2,267	622
Allowance for Loan and Lease Losses, Adjustments, Other	(24)	1,645
Allowance for Loan and Lease Losses Write-offs, Net	0	0
Total ending balance	2,243	2,267
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	22	21
Allowance for Loan and Lease Losses, Adjustments, Other	13	1
Allowance for Loan and Lease Losses Write-offs, Net	0	0
Total ending balance	$ 35	$ 22