Variable Interest Entities (Summary) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Variable Interest Entity [Line Items]
Assets	$ 155,753.8	$ 150,783.1
Liabilities	143,004.8	138,885.2
Other Assets
Variable Interest Entity [Line Items]
Investment Carrying Amount	823.2	889.1
Other Assets | Affordable Housing
Variable Interest Entity [Line Items]
Investment Carrying Amount	599.3	622.8
Other Assets | New Markets
Variable Interest Entity [Line Items]
Investment Carrying Amount	223.9	266.3
Other Liabilities
Variable Interest Entity [Line Items]
Unfunded Commitments	173.4	178.8
Other Liabilities | Affordable Housing
Variable Interest Entity [Line Items]
Unfunded Commitments	173.4	178.8
Other Liabilities | New Markets
Variable Interest Entity [Line Items]
Unfunded Commitments	0.0	0.0
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	795.0	857.0
Liabilities	$ 167.3	$ 172.0