Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,321.5	$ 2,435.4
Mortgage Loans, Percent of Total	100.00%	100.00%
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,351.8	$ 1,389.6
Mortgage Loans, Percent of Total	58.30%	57.00%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 762.4	$ 937.2
Mortgage Loans, Percent of Total	32.80%	38.50%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 137.9	$ 75.0
Mortgage Loans, Percent of Total	5.90%	3.10%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 69.4	$ 33.6
Mortgage Loans, Percent of Total	3.00%	1.40%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 85.9	$ 92.3
Mortgage Loans, Percent of Total	3.70%	3.80%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 885.4	$ 843.9
Mortgage Loans, Percent of Total	38.10%	34.60%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,309.1	$ 1,458.0
Mortgage Loans, Percent of Total	56.40%	59.90%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 41.1	$ 41.2
Mortgage Loans, Percent of Total	1.80%	1.70%