Variable Interest Entities (Summary) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Variable Interest Entity [Line Items]
Assets	$ 156,797.1	$ 150,783.1
Liabilities	144,141.3	138,885.2
Other Assets
Variable Interest Entity [Line Items]
Investment Carrying Amount	852.6	889.1
Other Assets | Affordable Housing
Variable Interest Entity [Line Items]
Investment Carrying Amount	593.9	622.8
Other Assets | New Markets
Variable Interest Entity [Line Items]
Investment Carrying Amount	258.7	266.3
Other Liabilities
Variable Interest Entity [Line Items]
Unfunded Commitments	162.9	178.8
Other Liabilities | Affordable Housing
Variable Interest Entity [Line Items]
Unfunded Commitments	162.9	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	823.1	857.0
Liabilities	$ 157.5	$ 172.0