Variable Interest Entities (Summary) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
Assets	$ 151,108.0	$ 155,036.7
Liabilities	139,520.2	143,777.2
Other Assets
Variable Interest Entity [Line Items]
Total investment carrying amount	914.8	904.3
Other Assets | Affordable Housing
Variable Interest Entity [Line Items]
Total investment carrying amount	651.1	635.9
Other Assets | Other Community Development
Variable Interest Entity [Line Items]
Total investment carrying amount	263.7	268.4
Other Liabilities
Variable Interest Entity [Line Items]
Total unfunded commitments	220.1	218.9
Other Liabilities | Affordable Housing
Variable Interest Entity [Line Items]
Total unfunded commitments	220.1	218.9
Other Liabilities | Other Community Development
Variable Interest Entity [Line Items]
Total unfunded commitments	0.0	0.0
Variable Interest Entity, Not Primary Beneficiary | Other Assets
Variable Interest Entity [Line Items]
Assets	879.0	867.2
Variable Interest Entity, Not Primary Beneficiary | Other Liabilities
Variable Interest Entity [Line Items]
Liabilities	$ 213.0	$ 210.1