Mortgage Loans, Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2026	Mar. 31, 2025
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Beginning Balance		$ 15.9
Financing Receivable, Allowance for Credit Loss, Ending Balance		15.3
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	15.9	$ 16.1
Current Period Provisions	[1]	(0.6)	0.5
Write-offs	[1]	0.0	0.0
Recoveries	[1]	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	15.3	16.6
Commercial Real Estate | Loan to Value Ratio Below or Equal to 65 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	4.3	4.2
Current Period Provisions	[1]	(0.2)	(0.4)
Write-offs	[1]	0.0	0.0
Recoveries	[1]	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	4.1	3.8
Commercial Real Estate | Loan To Value Ratio Above 65 To 75 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	0.7	1.7
Current Period Provisions	[1]	(0.1)	0.0
Write-offs	[1]	0.0	0.0
Recoveries	[1]	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	0.6	1.7
Commercial Real Estate | Loan To Value Ratio Above 75 To 85 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	1.9	2.2
Current Period Provisions	[1]	(0.5)	0.9
Write-offs	[1]	0.0	0.0
Recoveries	[1]	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	1.4	3.1
Commercial Real Estate | Loan To Value Ratio Above 85 Percent
Financing Receivable, Allowance for Credit Loss
Financing Receivable, Allowance for Credit Loss, Beginning Balance	[1]	9.0	8.0
Current Period Provisions	[1]	0.2	0.0
Write-offs	[1]	0.0	0.0
Recoveries	[1]	0.0	0.0
Financing Receivable, Allowance for Credit Loss, Ending Balance	[1]	$ 9.2	$ 8.0

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