Investments Investments (Analysis of Past Due Commercial Mortgage, Agricultural and Other Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Current	$ 1,773,152	$ 1,474,185
Total Loans	1,773,152	1,474,185
Non-Accrual Status	0	0
30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Commercial Mortgage Loans
Financing Receivable, Past Due [Line Items]
Current	1,668,578	1,414,139
Total Loans	1,668,578	1,414,139
Non-Accrual Status	0	0
Commercial Mortgage Loans | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Commercial Mortgage Loans | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Commercial Mortgage Loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Agricultural Property Loans
Financing Receivable, Past Due [Line Items]
Current	104,574	60,046
Total Loans	104,574	60,046
Non-Accrual Status	0	0
Agricultural Property Loans | 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Agricultural Property Loans | 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Agricultural Property Loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Accruing Interest	$ 0	$ 0