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, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income	$ 349.9	$ 529.2
Interest Expense	9.8	121.1
Other Operating Income	54.9	34.4
INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(1.6)	(0.5)
Gains (Losses) on cash flow hedges recognized on	5.5	4.1
INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	7.0	(2.9)
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	(1.0)	(0.1)
Interest Rate Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	18.4	(76.0)
Recognized on hedged items	(18.4)	76.0
Amounts related to interest settlements on derivatives	(1.6)	(0.5)
Interest Rate Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(142.9)	150.4
Recognized on hedged items	142.9	(150.4)
Amounts related to interest settlements on derivatives	7.0	(2.9)
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	4.1
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	$ (1.0)	$ (0.1)

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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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, 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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