Variable Interest Entities (Summary) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
Assets	$ 156,752.5	$ 155,036.7
Liabilities	145,116.8	143,777.2
Other Assets
Variable Interest Entity [Line Items]
Total investment carrying amount	915.3	904.3
Other Assets | Affordable Housing
Variable Interest Entity [Line Items]
Total investment carrying amount	656.3	635.9
Other Assets | Other Community Development
Variable Interest Entity [Line Items]
Total investment carrying amount	259.0	268.4
Other Liabilities
Variable Interest Entity [Line Items]
Total unfunded commitments	219.1	218.9
Other Liabilities | Affordable Housing
Variable Interest Entity [Line Items]
Total unfunded commitments	219.1	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	880.8	867.2
Variable Interest Entity, Not Primary Beneficiary | Other Liabilities
Variable Interest Entity [Line Items]
Liabilities	$ 212.1	$ 210.1