Schedule of Participating Mortgage Loans by Internal Credit Rating and Loan to Value (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Mortgage Loans on Real Estate
Mortgage Loans	$ 2,560.4	$ 2,432.1
Percent of Total	100.00%	100.00%
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,346.1	$ 1,189.4
Percent of Total	52.60%	48.90%
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,076.8	$ 1,000.3
Percent of Total	42.00%	41.10%
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 114.9	$ 155.8
Percent of Total	4.50%	6.40%
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans	$ 22.6	$ 86.6
Percent of Total	0.90%	3.60%
Total
Mortgage Loans on Real Estate
Percent of Total	100.00%	100.00%
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 27.3	$ 3.5
Percent of Total	1.10%	0.10%
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 709.6	$ 510.0
Percent of Total	27.70%	21.00%
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 1,802.6	$ 1,863.0
Percent of Total	70.40%	76.60%
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 20.9	$ 39.4
Percent of Total	0.80%	1.60%
B Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans	$ 0.0	$ 16.2
Percent of Total	0.00%	0.70%
Total
Mortgage Loans on Real Estate
Percent of Total	100.00%	100.00%