Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,238.9	$ 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	$ 1,527.0	$ 1,409.9
Mortgage Loans, Percent of Total	68.20%	60.80%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 481.6	$ 707.0
Mortgage Loans, Percent of Total	21.50%	30.50%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 148.5	$ 136.5
Mortgage Loans, Percent of Total	6.60%	5.90%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 81.8	$ 64.8
Mortgage Loans, Percent of Total	3.70%	2.80%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 94.5	$ 85.2
Mortgage Loans, Percent of Total	4.20%	3.70%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 982.2	$ 942.5
Mortgage Loans, Percent of Total	43.90%	40.60%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,064.4	$ 1,249.5
Mortgage Loans, Percent of Total	47.50%	53.90%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 97.8	$ 41.0
Mortgage Loans, Percent of Total	4.40%	1.80%