Investments (Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 7,260,422	$ 6,155,050
Commercial mortgage loans, Percentage	100.00%	100.00%
Allowance for Credit Losses	$ (44,309)	$ (37,689)
Commercial Mortgage Loans	7,223,568	6,122,721
Total net Commercial Mortgage and Other Loans	7,223,568	6,122,721
Other loans	7,455	5,360
Commercial Mortgage and Agricultural Loans
Commercial Mortgage and Other Loans [Line Items]
Commercial Mortgage Loans	7,216,113	6,117,361
Total net Commercial Mortgage and Other Loans	7,216,113	6,117,361
Other Collateralized Loans
Commercial Mortgage and Other Loans [Line Items]
Other loans	7,455	5,360
Total Net Commercial Mortgage and Other Loans
Commercial Mortgage and Other Loans [Line Items]
Commercial Mortgage Loans	7,223,568	6,122,721
Total net Commercial Mortgage and Other Loans	7,223,568	6,122,721
Apartments and multi-family
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 1,892,110	$ 1,578,785
Commercial mortgage loans, Percentage	26.10%	25.70%
Hospitality
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 100,890	$ 102,952
Commercial mortgage loans, Percentage	1.40%	1.70%
Industrial
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 2,865,789	$ 2,486,230
Commercial mortgage loans, Percentage	39.50%	40.40%
Office
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 597,283	$ 604,611
Commercial mortgage loans, Percentage	8.20%	9.80%
Other
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 694,191	$ 456,720
Commercial mortgage loans, Percentage	9.60%	7.40%
Retail
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 406,850	$ 363,706
Commercial mortgage loans, Percentage	5.50%	5.90%
Commercial mortgage loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 6,557,113	$ 5,593,004
Commercial mortgage loans, Percentage	90.30%	90.90%
Agricultural property loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 703,309	$ 562,046
Commercial mortgage loans, Percentage	9.70%	9.10%