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	$ 2,065	$ 1,794
Addition to (release of) allowance for credit losses	(7)	271
Charge-offs, net of recoveries	0	0
Total ending balance	2,058	2,065
Commercial Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	2,026	1,728
Addition to (release of) allowance for credit losses	(10)	298
Charge-offs, net of recoveries	0	0
Total ending balance	2,016	2,026
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	39	66
Addition to (release of) allowance for credit losses	3	(27)
Charge-offs, net of recoveries	0	0
Total ending balance	$ 42	$ 39