Net Interest Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Interest Income
Federal Reserve and Other Central Bank Deposits	$ 326.5	$ 451.7	$ 1,142.9	$ 1,369.0
Interest-Bearing Due from and Deposits with Banks	20.7	28.5	65.9	94.5
Federal Funds Sold and Securities Purchased under Agreements to Resell	711.7	890.8	2,091.7	2,578.2
Securities — Taxable	481.1	486.3	1,398.3	1,409.0
Securities - Non-Taxable	0.2	0.2	0.8	0.8
Loans	584.6	644.5	1,735.8	1,946.4
Other Interest-Earning Assets	19.5	28.2	62.6	84.4
Total Interest Income	2,144.3	2,530.2	6,498.0	7,482.3
Interest Expense
Deposits	658.4	873.5	2,082.3	2,653.5
Federal Funds Purchased	24.8	29.6	72.8	101.9
Securities Sold Under Agreements to Repurchase	695.0	869.7	2,048.8	2,535.1
Other Borrowings	79.6	94.8	239.7	278.7
Senior Notes	39.3	44.2	117.1	132.4
Long-Term Debt	56.4	56.1	167.9	167.4
Total Interest Expense	1,553.5	1,967.9	4,728.6	5,869.0
Net Interest Income	$ 590.8	$ 562.3	$ 1,769.4	$ 1,613.3

Interest expense incurred during the reporting period on senior notes.

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Interest Income, Federal Reserve Deposits and Other

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Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein.

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The aggregate interest and fee income generated by: (1) loans the Entity has positive intent and ability to hold for the foreseeable future, or until maturity or payoff, including commercial and consumer loans, whether domestic or foreign, which may consist of: (a) industrial and agricultural; (b) real estate; and (c) real estate construction loans; (d) trade financing; (e) lease financing; (f) home equity lines-of-credit; (g) automobile and other vehicle loans; and (h) credit card and other revolving-type loans and (2) loans and leases held-for-sale which may include mortgage loans, direct financing, and sales-type leases.

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Aggregate amount of interest expense on all deposits.

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Gross expenses on the purchase of Federal funds at a specified price with a simultaneous agreement to sell the same to the same counterparty at a fixed or determinable price at a future date.

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Amount of interest expense classified as operating.

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Amount of interest expense incurred on long-term debt classified as other, including, but not limited to, interest on long-term notes and amortization of issuance costs.

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Interest expense incurred during the reporting period on other short-term borrowings.

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Gross expenses on securities sold coupled with an agreement to repurchase the same from the same counterparty at a fixed or determinable price within a fixed or variable time period.

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Interest income derived from funds deposited with both domestic and foreign financial institutions including funds in money market and other accounts.

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Amount of interest income (expense) classified as operating.

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The aggregate interest income earned from (1) the lending of excess federal funds to another commercial bank requiring such for its legal reserve requirements and (2) securities purchased under agreements to resell.

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities exempt from state, federal and other income tax.

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

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Amount, after discount, accretion and premium amortization, of interest income and dividend income classified as other.

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