Net Interest Income (Net Interest Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest Income
Federal Reserve and Other Central Bank Deposits	$ 1,462.3	$ 472.0	$ 11.3
Interest-Bearing Due from and Deposits with Banks	130.1	46.6	9.1
Federal Funds Sold	0.3	0.1	0.0
Securities Purchased under Agreements to Resell	1,585.2	103.7	3.5
Securities – Taxable	1,534.4	899.9	658.8
Securities - Non-Taxable	1.3	1.3	1.5
Loans and Leases	2,551.1	1,344.3	713.5
Other Interest-Earning Assets	60.3	9.8	8.8
Total Interest Income	7,325.0	2,877.7	1,406.5
Interest Expense
Deposits	2,685.3	602.8	(61.3)
Federal Funds Purchased	256.9	34.1	(0.4)
Securities Sold under Agreements to Repurchase	1,541.1	90.7	0.2
Other Borrowings	542.5	126.2	14.2
Senior Notes	170.0	92.7	48.3
Long-Term Debt	147.2	44.0	21.1
Floating Rate Capital Debt	0.0	0.0	1.7
Total Interest Expense	5,343.0	990.5	23.8
Net Interest Income	$ 1,982.0	$ 1,887.2	$ 1,382.7