Investments (Allowance for Credit Losses) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	$ 2,896	$ 2,650
Addition to (release of) allowance for credit losses	(192)	246
Charge-offs, net of recoveries	0	0
Total ending balance	2,704	2,896
Commercial Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	2,861	2,616
Addition to (release of) allowance for credit losses	(205)	245
Charge-offs, net of recoveries	0	0
Total ending balance	2,656	2,861
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	35	34
Addition to (release of) allowance for credit losses	13	1
Charge-offs, net of recoveries	0	0
Total ending balance	$ 48	$ 35