Derivative Financial Instruments (Location and Amount of Fair Value And Cash Flow Hedge Derivative Gains And Losses Recorded In Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income	$ 2,445.6	$ 1,455.4
Interest Expense	1,917.5	924.2
Other Operating Income	61.0	46.8
INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	22.3	12.3
Gains (Losses) on cash flow hedges recognized on	5.5	0.0
INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(19.9)	(18.4)
Gains (Losses) on cash flow hedges recognized on	0.0	0.0
OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	0.0	0.0
Gains (Losses) on cash flow hedges recognized on	0.0	0.6
Interest Rate Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	123.0	(18.5)
Recognized on hedged items	(123.0)	18.5
Amounts related to interest settlements on derivatives	22.3	12.3
Interest Rate Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(30.1)	49.1
Recognized on hedged items	30.1	(49.1)
Amounts related to interest settlements on derivatives	(19.9)	(18.4)
Interest Rate Contracts \| OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	0.0	0.0
Recognized on hedged items	0.0	0.0
Amounts related to interest settlements on derivatives	0.0	0.0
Foreign Exchange Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	5.5	0.0
Foreign Exchange Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	0.0	0.0
Foreign Exchange Contracts \| OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	$ 0.0	$ 0.6

Change in Unrealized Gain (Loss) on Amounts Related to Settlement

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Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Total amount of gain (loss) derived from fair value hedges recognized in earnings in the period.

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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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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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