Investments (Allowance for Credit Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning of period	$ 7,382	$ 2,663
Cumulative effect of adoption of ASU 2016-13	0	3,157
Addition to (release of) allowance for expected losses	(381)	462
Allowance, end of period	7,001	6,282
Commercial Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning of period	7,116	2,622
Cumulative effect of adoption of ASU 2016-13	0	3,118
Addition to (release of) allowance for expected losses	(379)	363
Allowance, end of period	6,737	6,103
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning of period	266	41
Cumulative effect of adoption of ASU 2016-13	0	39
Addition to (release of) allowance for expected losses	(2)	99
Allowance, end of period	$ 264	$ 179