Investments (Schedule of Amortized Cost of Mortgage Participations and Other Loans by Credit Ratings and Year of Origination) (Details) $ in Millions	Dec. 31, 2022 USD ($)
Schedule of Investments [Line Items]
Allowance for credit losses	$ (3.2)
Amortized cost, net of allowance for credit losses	388.6
Amortized Cost
Schedule of Investments [Line Items]
Prior to 2018	203.6
2018	36.0
2019	47.2
2020	33.3
2021	61.7
2022	10.0
Total	391.8
Aaa/Aa/A
Schedule of Investments [Line Items]
Prior to 2018	137.7
2018	36.0
2019	47.2
2020	27.3
2021	61.7
2022	10.0
Total	319.9
Baa
Schedule of Investments [Line Items]
Prior to 2018	37.4
Total	37.4
Ba and lower
Schedule of Investments [Line Items]
Prior to 2018	28.5
2020	6.0
Total	$ 34.5