Investments (Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 5,404,371	$ 4,948,943
Commercial mortgage loans, Percentage	100.00%	100.00%
Allowance for Credit Losses	$ (22,093)	$ (20,263)
Commercial Mortgage Loans	5,382,278	4,928,680
Commercial Mortgage and Agricultural Loans
Commercial Mortgage and Other Loans [Line Items]
Commercial Mortgage Loans	5,382,278	4,928,680
Apartments and multi-family
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 1,438,086	$ 1,289,026
Commercial mortgage loans, Percentage	26.60%	26.00%
Hospitality
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 103,254	$ 104,177
Commercial mortgage loans, Percentage	1.90%	2.10%
Industrial
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 2,024,002	$ 1,766,247
Commercial mortgage loans, Percentage	37.50%	35.80%
Office
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 588,424	$ 590,897
Commercial mortgage loans, Percentage	10.90%	11.90%
Other
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 401,375	$ 380,121
Commercial mortgage loans, Percentage	7.40%	7.70%
Retail
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 368,990	$ 351,457
Commercial mortgage loans, Percentage	6.80%	7.10%
Commercial mortgage loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 4,924,131	$ 4,481,925
Commercial mortgage loans, Percentage	91.10%	90.60%
Agricultural property loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 480,240	$ 467,018
Commercial mortgage loans, Percentage	8.90%	9.40%