Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,390.0	$ 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	$ 1,352.1	$ 1,389.6
Mortgage Loans, Percent of Total	56.60%	57.00%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 917.8	$ 937.2
Mortgage Loans, Percent of Total	38.40%	38.50%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 91.5	$ 75.0
Mortgage Loans, Percent of Total	3.80%	3.10%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 28.6	$ 33.6
Mortgage Loans, Percent of Total	1.20%	1.40%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 80.2	$ 92.3
Mortgage Loans, Percent of Total	3.40%	3.80%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 803.7	$ 843.9
Mortgage Loans, Percent of Total	33.60%	34.60%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,465.2	$ 1,458.0
Mortgage Loans, Percent of Total	61.30%	59.90%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 40.9	$ 41.2
Mortgage Loans, Percent of Total	1.70%	1.70%