Derivative Financial Instruments (Location and Amount of Gains and Losses Recorded in Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income	$ 529.2	$ 662.8
Interest Expense	121.1	240.8
Other Operating Income	34.4	29.0
INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(0.5)	5.5
Gains (Losses) on cash flow hedges recognized on	4.1	14.2
INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(2.9)	(1.6)
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	(0.1)	(0.6)
Interest Rate Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(76.0)	(35.4)
Recognized on hedged items	76.0	35.4
Amounts related to interest settlements on derivatives	(0.5)	5.5
Gains (Losses) on cash flow hedges recognized on	0.0	(0.2)
Interest Rate Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	150.4	28.5
Recognized on hedged items	(150.4)	(28.5)
Amounts related to interest settlements on derivatives	(2.9)	(1.6)
Gains (Losses) on cash flow hedges recognized on	0.0	0.0
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
Gains (Losses) on cash flow hedges recognized on	0.0	0.0
Foreign Exchange Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	4.1	14.4
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	$ (0.1)	$ (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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