Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,490.7	$ 2,560.4
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,296.3	$ 1,346.1
Mortgage Loans, Percent of Total	52.10%	52.60%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,091.4	$ 1,076.8
Mortgage Loans, Percent of Total	43.80%	42.00%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 90.8	$ 114.9
Mortgage Loans, Percent of Total	3.60%	4.50%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 12.2	$ 22.6
Mortgage Loans, Percent of Total	0.50%	0.90%
Total
Mortgage Loans on Real Estate
Mortgage Loans, Percent of Total	100.00%	100.00%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 30.2	$ 27.3
Mortgage Loans, Percent of Total	1.20%	1.10%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 696.8	$ 709.6
Mortgage Loans, Percent of Total	28.00%	27.70%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 1,743.3	$ 1,802.6
Mortgage Loans, Percent of Total	70.00%	70.40%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 20.4	$ 20.9
Mortgage Loans, Percent of Total	0.80%	0.80%
Total
Mortgage Loans on Real Estate
Mortgage Loans, Percent of Total	100.00%	100.00%