Investments (Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 8,699,465	$ 7,785,059
Commercial mortgage loans, Percentage	100.00%	100.00%
Allowance for Credit Losses	$ (38,516)	$ (37,715)
Commercial Mortgage Loans	8,671,415	7,759,323
Total net Commercial Mortgage and Other Loans	8,671,415	7,759,323
Other loans	10,466	11,979
Commercial Mortgage and Agricultural Loans
Commercial Mortgage and Other Loans [Line Items]
Commercial Mortgage Loans	8,660,949	7,747,344
Total net Commercial Mortgage and Other Loans	8,660,949	7,747,344
Other Collateralized Loans
Commercial Mortgage and Other Loans [Line Items]
Other loans	10,466	11,979
Total Net Commercial Mortgage and Other Loans
Commercial Mortgage and Other Loans [Line Items]
Commercial Mortgage Loans	8,671,415	7,759,323
Total net Commercial Mortgage and Other Loans	8,671,415	7,759,323
Apartments and multi-family
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 2,225,011	$ 1,949,926
Commercial mortgage loans, Percentage	25.60%	25.00%
Health Care Senior Living
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 135,672	$ 134,195
Commercial mortgage loans, Percentage	1.60%	1.70%
Hospitality
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 94,557	$ 97,603
Commercial mortgage loans, Percentage	1.10%	1.30%
Industrial
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 3,287,343	$ 2,906,413
Commercial mortgage loans, Percentage	37.70%	37.30%
Office
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 526,692	$ 556,586
Commercial mortgage loans, Percentage	6.10%	7.10%
Retail
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 727,657	$ 693,949
Commercial mortgage loans, Percentage	8.30%	9.00%
Self-Storage
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 738,071	$ 543,701
Commercial mortgage loans, Percentage	8.50%	7.00%
Other
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 72,463	$ 72,645
Commercial mortgage loans, Percentage	0.80%	0.90%
Commercial mortgage loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 7,807,466	$ 6,955,018
Commercial mortgage loans, Percentage	89.70%	89.30%
Agricultural property loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 891,999	$ 830,041
Commercial mortgage loans, Percentage	10.30%	10.70%