Net Interest Income (Net Interest Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Interest Income
Federal Reserve and Other Central Bank Deposits	$ 398.9	$ 59.2	$ 775.9	$ 76.8
Interest-Bearing Due from and Deposits with Banks	32.1	6.5	60.3	9.1
Federal Funds Sold	0.1	0.0	0.3	0.0
Securities Purchased under Agreements to Resell	284.3	7.0	410.2	7.9
Securities — Taxable	366.3	193.7	704.1	362.7
Securities - Non-Taxable	0.4	0.3	0.7	0.7
Loans and Leases	639.2	256.4	1,217.4	447.6
Other Interest-Earning Assets	13.7	1.7	21.5	3.5
Total Interest Income	1,735.0	524.8	3,190.4	908.3
Interest Expense
Deposits	633.5	23.2	1,198.1	7.3
Federal Funds Purchased	87.6	2.8	127.7	2.8
Securities Sold Under Agreements to Repurchase	273.4	6.0	389.5	6.3
Other Borrowings	156.5	8.4	291.5	11.5
Senior Notes	42.1	18.9	81.3	28.5
Long-Term Debt	30.4	6.8	59.6	12.2
Total Interest Expense	1,223.5	66.1	2,147.7	68.6
Net Interest Income	$ 511.5	$ 458.7	$ 1,042.7	$ 839.7