Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,298.8	$ 2,318.2
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	$ 1,443.9	$ 1,409.9
Mortgage Loans, Percent of Total	62.80%	60.80%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 656.1	$ 707.0
Mortgage Loans, Percent of Total	28.50%	30.50%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 135.5	$ 136.5
Mortgage Loans, Percent of Total	5.90%	5.90%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 63.3	$ 64.8
Mortgage Loans, Percent of Total	2.80%	2.80%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 84.4	$ 85.2
Mortgage Loans, Percent of Total	3.70%	3.70%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,010.8	$ 942.5
Mortgage Loans, Percent of Total	44.00%	40.60%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,163.9	$ 1,249.5
Mortgage Loans, Percent of Total	50.60%	53.90%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 39.7	$ 41.0
Mortgage Loans, Percent of Total	1.70%	1.80%