Investments (Debt Service Coverage Ratio) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,554,777	$ 1,414,139
Commercial Mortgage Loans | ≥ 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,501,432	1,361,868
Commercial Mortgage Loans | 1.0X to 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	50,597	52,271
Commercial Mortgage Loans | Less than 1.0X
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,748	0
Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	92,514	60,046
Agricultural Property Loans | ≥ 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	88,916	56,437
Agricultural Property Loans | 1.0X to 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Agricultural Property Loans | Less than 1.0X
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 3,598	$ 3,609