Investments (Allowance for Credit Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning of period	$ 5,583	$ 6,879	$ 7,382	$ 2,663
Cumulative effect of adoption of ASU 2016-13			0	3,157
Addition to (release of) allowance for expected losses	(1,349)	754	(3,148)	1,813
Allowance, end of period	4,234	7,633	4,234	7,633
Commercial Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning of period	5,392	6,701	7,116	2,622
Cumulative effect of adoption of ASU 2016-13			0	3,118
Addition to (release of) allowance for expected losses	(1,236)	646	(2,960)	1,607
Allowance, end of period	4,156	7,347	4,156	7,347
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning of period	191	178	266	41
Cumulative effect of adoption of ASU 2016-13			0	39
Addition to (release of) allowance for expected losses	(113)	108	(188)	206
Allowance, end of period	$ 78	$ 286	$ 78	$ 286