Investments (Loan-to-value ratios) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 2,198
2019	34,083
2018	1,498
2017	12,750
2016	12,963
Prior	72,407
Revolving Loans	0
Recording investment gross of allowance for credit losses	135,899
Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	2,472
Revolving Loans	0
Recording investment gross of allowance for credit losses	2,472
Commercial Mortgage and Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,198
2019	34,083
2018	1,498
2017	12,750
2016	12,963
Prior	74,879
Revolving Loans	0
Recording investment gross of allowance for credit losses	138,371
0% to 59.99% \| Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	10,307
2018	0
2017	8,804
2016	9,771
Prior	58,521
Revolving Loans	0
Recording investment gross of allowance for credit losses	87,403
0% to 59.99% \| Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	2,472
Revolving Loans	0
Recording investment gross of allowance for credit losses	2,472
0% to 59.99% \| Commercial Mortgage and Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	10,307
2018	0
2017	8,804
2016	9,771
Prior	60,993
Revolving Loans	0
Recording investment gross of allowance for credit losses	89,875
60% to 69.99% \| Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,198
2019	20,727
2018	1,498
2017	3,946
2016	3,192
Prior	13,886
Revolving Loans	0
Recording investment gross of allowance for credit losses	45,447
60% to 69.99% \| Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	0
60% to 69.99% \| Commercial Mortgage and Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,198
2019	20,727
2018	1,498
2017	3,946
2016	3,192
Prior	13,886
Revolving Loans	0
Recording investment gross of allowance for credit losses	45,447
70% to 79.99% \| Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	3,049
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	3,049
70% to 79.99% \| Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	0
70% to 79.99% \| Commercial Mortgage and Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	3,049
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	3,049
80% or greater \| Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	0
80% or greater \| Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	0
80% or greater \| Commercial Mortgage and Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	0
Commercial Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Recording investment gross of allowance for credit losses	135,899	$ 139,803
Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Recording investment gross of allowance for credit losses	$ 2,472	$ 3,460

Amount of financing receivable originated more than five years prior to current fiscal year.

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Amount of financing receivable originated in current fiscal year.

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Amount of financing receivable originated in fiscal year prior to current fiscal year.

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Amount, before allowance for credit loss, of financing receivable.

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