Variable Interest Entities (Summary of Unconsolidated Tax Structures) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Variable Interest Entity [Line Items]
Investment Carrying Amount	$ 941.7	$ 876.7
Unfunded Commitments	319.2	227.1
Affordable Housing
Variable Interest Entity [Line Items]
Investment Carrying Amount	751.3	657.0
Unfunded Commitments	319.2	227.1
New Markets
Variable Interest Entity [Line Items]
Investment Carrying Amount	190.4	219.7
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Investment Carrying Amount	918.1	849.3
Unfunded Commitments	$ 315.9	$ 221.0