Derivative Financial Instruments - Effect on Statement of Comprehensive Income and Statement of Income (Details) - Designated as Hedging Instrument - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Derivatives in Net Investment Hedging Relationship
Derivative [Line Items]
Gain (Loss) Recorded in Other Comprehensive Income	$ 14.5	$ (11.4)
Gain Reclassified from Accumulated Other Comprehensive Loss into Earnings	0.6	0.5
Gain (Loss) Recorded in Earnings from Excluded Components	2.8	13.9
Derivatives in Net Investment Hedging Relationship \| Forward contracts
Derivative [Line Items]
Gain (Loss) Recorded in Other Comprehensive Income	65.4	(21.7)
Gain Reclassified from Accumulated Other Comprehensive Loss into Earnings	0.6	0.5
Gain (Loss) Recorded in Earnings from Excluded Components	2.8	13.9
Derivatives in Net Investment Hedging Relationship \| Put options
Derivative [Line Items]
Gain (Loss) Recorded in Other Comprehensive Income	(47.7)	29.3
Gain Reclassified from Accumulated Other Comprehensive Loss into Earnings	0.0	0.0
Gain (Loss) Recorded in Earnings from Excluded Components	0.0	0.0
Derivatives in Net Investment Hedging Relationship \| Call options
Derivative [Line Items]
Gain (Loss) Recorded in Other Comprehensive Income	(1.3)	(19.0)
Gain Reclassified from Accumulated Other Comprehensive Loss into Earnings	0.0	0.0
Gain (Loss) Recorded in Earnings from Excluded Components	0.0	0.0
Cash Flow Hedging \| Interest rate swap
Derivative [Line Items]
Gain (Loss) Recorded in Other Comprehensive Income	(1.9)	0.0
Gain Reclassified from Accumulated Other Comprehensive Loss into Earnings	0.0	0.0
Gain (Loss) Recorded in Earnings from Excluded Components	$ 0.0	$ 0.0

Gain (Loss) On Derivative Used In Cash Flow Hedge And Net Investment Hedge, After Tax

No definition available.

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- Definition

Other Comprehensive Income (Loss), Cash Flow Hedge And Net Investment Hedge, Gain (Loss), After Reclassification And Tax, Parent

+ References

No definition available.

+ Details

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- Definition

Other Comprehensive Income (Loss), Net Investment Hedge, Gain (Loss), After Reclassification And Tax, Parent

+ References

No definition available.

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- Definition

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.

+ References

No definition available.

+ Details

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- Definition

The net gain (loss) recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959

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- Definition

Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness, attributable to parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580

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- Definition

Amount, before tax and adjustments, of gain (loss) from increase (decrease) in value of excluded component of derivative designated and qualifying as hedge. Adjustments include, but are not limited to, reclassifications for sale and settlement, and amounts recognized under systematic and rational method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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- Definition

Amount, after tax, of reclassification from accumulated other comprehensive income (AOCI) of gain (loss) from increase (decrease) in fair value of net investment hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CCC
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-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998896-113959

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