Accumulated Other Comprehensive Income (Loss) (Details of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
BEFORE TAX
Net Change	$ (468.0)	$ 338.3
TAX EFFECT
Net Change	105.9	(98.6)
AFTER TAX
Net Change	(362.1)	239.7
Unrealized Gains (Losses) on Debt Securities Available for Sale
BEFORE TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	(496.5)	266.8
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.0	0.0
Net Change	(496.5)	266.8
TAX EFFECT
Unrealized Gains (Losses) on Debt Securities Available for Sale	126.8	(67.1)
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.0	0.0
Net Change	126.8	(67.1)
AFTER TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	(369.7)	199.7
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.0	0.0
Net Change	(369.7)	199.7
Unrealized Gains (Losses) on Cash Flow Hedges
BEFORE TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	(4.5)	(4.0)
Net Change	(7.0)	9.7
TAX EFFECT
Reclassification Adjustment for (Gains) Losses Included in Net Income	1.1	1.0
Net Change	1.8	(2.4)
AFTER TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	(3.4)	(3.0)
Net Change	(5.2)	7.3
Foreign Currency Adjustments
BEFORE TAX
Net Change	25.2	52.3
TAX EFFECT
Net Change	(20.2)	(26.6)
AFTER TAX
Net Change	5.0	25.7
Foreign Currency Translation Adjustments
BEFORE TAX
Net Change	(57.3)	(89.8)
TAX EFFECT
Net Change	0.5	9.6
AFTER TAX
Net Change	(56.8)	(80.2)
Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses)
BEFORE TAX
Net Change	(0.2)	(0.6)
TAX EFFECT
Net Change	0.1	0.1
AFTER TAX
Net Change	(0.1)	(0.5)
Net Investment Hedge Gains (Losses)
BEFORE TAX
Net Change	82.7	142.7
TAX EFFECT
Net Change	(20.8)	(36.3)
AFTER TAX
Net Change	61.9	106.4
Pension and Other Postretirement Benefit Adjustments
BEFORE TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	(1.3)	(1.3)
Net Change	10.3	9.5
TAX EFFECT
Unrealized Gains (Losses) on Debt Securities Available for Sale	0.3	0.1
Net Change	(2.5)	(2.5)
AFTER TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	(1.0)	(1.2)
Net Change	7.8	7.0
Amortization of Net Actuarial Loss
BEFORE TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	11.9	10.9
TAX EFFECT
Reclassification Adjustment for (Gains) Losses Included in Net Income	(2.9)	(2.6)
AFTER TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	9.0	8.3
Amortization of Prior Service Cost
BEFORE TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.3)	(0.1)
TAX EFFECT
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.1	0.0
AFTER TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.2)	(0.1)
Foreign Exchange Contracts \| Unrealized Gains (Losses) on Cash Flow Hedges
BEFORE TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	(2.5)	13.3
TAX EFFECT
Unrealized Gains (Losses) on Debt Securities Available for Sale	0.7	(3.3)
AFTER TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	(1.8)	10.0
Interest Rate Contracts \| Unrealized Gains (Losses) on Cash Flow Hedges
BEFORE TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	0.0	0.4
TAX EFFECT
Unrealized Gains (Losses) on Debt Securities Available for Sale	0.0	(0.1)
AFTER TAX
Unrealized Gains (Losses) on Debt Securities Available for Sale	$ 0.0	$ 0.3

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