Investments (Analysis of Past Due Commercial Mortgage, Agricultural and Other Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	$ 7,797,038	$ 6,160,410
Non-Accrual Status	29,885	1,301
Current
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	7,767,876	6,160,410
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	0	0
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	2,505	0
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	26,657	0
Commercial mortgage loans
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	6,955,018	5,593,004
Non-Accrual Status	5,120	0
Commercial mortgage loans | Current
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	6,951,093	5,593,004
Commercial mortgage loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	0	0
Commercial mortgage loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	0	0
Commercial mortgage loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	3,925	0
Agricultural Loan
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	830,041	562,046
Non-Accrual Status	24,765	1,301
Agricultural Loan | Current
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	804,804	562,046
Agricultural Loan | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	0	0
Agricultural Loan | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	2,505	0
Agricultural Loan | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	22,732	0
Other Collateralized Loans
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	11,979	5,360
Non-Accrual Status	0	0
Other Collateralized Loans | Current
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	11,979	5,360
Other Collateralized Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	0	0
Other Collateralized Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	0	0
Other Collateralized Loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Recording investment gross of allowance for credit losses	0	0
Loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Accruing Interest	$ 0	$ 0