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	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income	$ 351.3	$ 355.4	$ 1,044.3	$ 1,290.9
Interest Expense	4.9	26.8	22.2	182.1
Other Operating Income	62.3	53.5	171.6	144.4
INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(10.6)	(14.2)	(14.2)	(11.6)
Gains (Losses) on cash flow hedges recognized on	0.3	4.4	8.5	11.1
INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	0.9	(2.5)	32.4	6.1
Gains (Losses) on cash flow hedges recognized on	0.0	0.0	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	0.0	0.0
Gains (Losses) on cash flow hedges recognized on	(1.0)	0.3	(4.5)	0.1
Interest Rate Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	9.3	15.1	27.2	(75.6)
Recognized on hedged items	(9.3)	(15.1)	(27.2)	75.6
Amounts related to interest settlements on derivatives	(10.6)	(14.2)	(14.2)	(11.6)
Gains (Losses) on cash flow hedges recognized on	0.0	0.2	0.0	0.3
Interest Rate Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(1.4)	(2.9)	(112.4)	152.1
Recognized on hedged items	1.4	2.9	112.4	(152.1)
Amounts related to interest settlements on derivatives	0.9	(2.5)	32.4	6.1
Gains (Losses) on cash flow hedges recognized on	0.0	0.0	0.0	0.0
Interest Rate Contracts \| OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	0.0	0.0	0.0	0.0
Recognized on hedged items	0.0	0.0	0.0	0.0
Amounts related to interest settlements on derivatives	0.0	0.0	0.0	0.0
Gains (Losses) on cash flow hedges recognized on	0.0	0.0	0.0	0.0
Foreign Exchange Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	0.3	4.2	8.5	10.8
Foreign Exchange Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	0.0	0.0	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)	$ 0.3	$ (4.5)	$ 0.1

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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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