Net Interest Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Interest Income
Federal Reserve and Other Central Bank Deposits	$ 451.7	$ 352.1	$ 1,369.0	$ 1,128.0
Interest-Bearing Due from and Deposits with Banks	28.5	34.9	94.5	95.2
Federal Funds Sold	0.0	0.0	0.0	0.3
Securities Purchased under Agreements to Resell	890.8	463.9	2,578.2	874.1
Securities — Taxable	486.3	402.4	1,409.0	1,106.5
Securities - Non-Taxable	0.2	0.3	0.8	1.0
Loans	644.5	664.2	1,946.4	1,881.6
Other Interest-Earning Assets	28.2	17.2	84.4	38.7
Total Interest Income	2,530.2	1,935.0	7,482.3	5,125.4
Interest Expense
Deposits	873.5	716.6	2,653.5	1,914.7
Federal Funds Purchased	29.6	77.5	101.9	205.2
Securities Sold Under Agreements to Repurchase	869.7	454.0	2,535.1	843.5
Other Borrowings	94.8	154.8	278.7	446.3
Senior Notes	44.2	44.1	132.4	125.4
Long-Term Debt	56.1	31.8	167.4	91.4
Total Interest Expense	1,967.9	1,478.8	5,869.0	3,626.5
Net Interest Income	$ 562.3	$ 456.2	$ 1,613.3	$ 1,498.9