Investments (Allowance for Credit Losses) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	$ 6,879	$ 2,663
Cumulative effect of adoption of ASU 2016-13		3,157
Addition to (release of) allowance for expected losses	754	1,813
Total ending balance	7,633	7,633
Commercial Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	6,701	2,622
Cumulative effect of adoption of ASU 2016-13		3,118
Addition to (release of) allowance for expected losses	646	1,607
Total ending balance	7,347	7,347
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	178	41
Cumulative effect of adoption of ASU 2016-13		39
Addition to (release of) allowance for expected losses	108	206
Total ending balance	286	286
Other Collateralized Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of year	0	0
Cumulative effect of adoption of ASU 2016-13		0
Addition to (release of) allowance for expected losses	0	0
Total ending balance	$ 0	$ 0