Mortgage Loans, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Current Period Provisions		$ (0.9)	$ 1.4	$ (0.5)	$ 1.9
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]			16.1
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	15.6		15.6
Commercial Real Estate | Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	3.8	3.6	4.2	3.8
Current Period Provisions	[1]	0.0	0.1	(0.4)	(0.1)
Write-offs	[1]	0.0	0.0	0.0	0.0
Recoveries	[1]	0.0	0.0	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	3.8	3.7	3.8	3.7
Commercial Real Estate | Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	1.7	3.4	1.7	3.8
Current Period Provisions	[1]	(0.2)	(0.1)	(0.2)	(0.5)
Write-offs	[1]	0.0	0.0	0.0	0.0
Recoveries	[1]	0.0	0.0	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	1.5	3.3	1.5	3.3
Commercial Real Estate | Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	3.1	1.2	2.2	1.2
Current Period Provisions	[1]	(2.0)	0.5	(1.1)	0.5
Write-offs	[1]	0.0	0.0	0.0	0.0
Recoveries	[1]	0.0	0.0	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	1.1	1.7	1.1	1.7
Commercial Real Estate | Loan To Value Ratio Above 85 Percent
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	8.0	2.5	8.0	1.4
Current Period Provisions	[1]	1.2	0.9	1.2	2.0
Write-offs	[1]	0.0	0.0	0.0	0.0
Recoveries	[1]	0.0	0.0	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	9.2	3.4	9.2	3.4
Commercial Real Estate | Loan to Value Ratio Total
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	16.6	10.7	16.1	10.2
Current Period Provisions	[1]	(1.0)	1.4	(0.5)	1.9
Write-offs	[1]	0.0	0.0	0.0	0.0
Recoveries	[1]	0.0	0.0	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	$ 15.6	$ 12.1	$ 15.6	$ 12.1

[1] 1Loan-to-Value Ratio utilizes the most recent internal valuation of the property