Variable Interest Entities (Summary of Unconsolidated Tax Structures) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Variable Interest Entity [Line Items]
Investment Carrying Amount	$ 1,000.0	$ 1,026.9
Unfunded Commitments	364.9	373.0
Affordable Housing
Variable Interest Entity [Line Items]
Investment Carrying Amount	810.5	834.0
Unfunded Commitments	364.9	373.0
New Markets
Variable Interest Entity [Line Items]
Investment Carrying Amount	189.5	192.9
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Investment Carrying Amount	978.8	1,000.0
Unfunded Commitments	$ 361.7	$ 369.7