Net Interest Income (Net Interest Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Interest Income
Federal Reserve and Other Central Bank Deposits	$ 352.1	$ 135.4	$ 1,128.0	$ 212.2
Interest-Bearing Due from and Deposits with Banks	34.9	14.5	95.2	23.6
Federal Funds Sold	0.0	0.0	0.3	0.0
Securities Purchased under Agreements to Resell	463.9	30.5	874.1	38.4
Securities — Taxable	402.4	237.0	1,106.5	599.7
Securities - Non-Taxable	0.3	0.4	1.0	1.1
Loans and Leases	664.2	379.8	1,881.6	827.4
Other Interest-Earning Assets	17.2	1.7	38.7	5.2
Total Interest Income	1,935.0	799.3	5,125.4	1,707.6
Interest Expense
Deposits	716.6	177.3	1,914.7	184.6
Federal Funds Purchased	77.5	9.9	205.2	12.7
Securities Sold Under Agreements to Repurchase	454.0	25.5	843.5	31.8
Other Borrowings	154.8	35.7	446.3	47.2
Senior Notes	44.1	28.6	125.4	57.1
Long-Term Debt	31.8	9.3	91.4	21.5
Total Interest Expense	1,478.8	286.3	3,626.5	354.9
Net Interest Income	$ 456.2	$ 513.0	$ 1,498.9	$ 1,352.7