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Goodwill and Other Intangible Assets - Intangible Assets by Asset Type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,844.5	$ 2,803.0
Accumulated Amortization	(2,399.4)	(2,208.9)
Net Carrying Amount	445.1	594.1
Customer relationships and contracts
Intangible Assets [Line Items]
Gross Carrying Amount	2,131.5	2,111.2
Accumulated Amortization	(1,927.9)	(1,786.4)
Net Carrying Amount	$ 203.6	$ 324.8
Trade name
Intangible Assets [Line Items]
Useful Life (Years)	20 years	20 years
Gross Carrying Amount	$ 422.8	$ 422.8
Accumulated Amortization	(280.1)	(259.0)
Net Carrying Amount	142.7	163.8
Internally developed software
Intangible Assets [Line Items]
Gross Carrying Amount	280.6	263.5
Accumulated Amortization	(186.0)	(160.0)
Net Carrying Amount	94.6	103.5
Other
Intangible Assets [Line Items]
Gross Carrying Amount	9.6	5.5
Accumulated Amortization	(5.4)	(3.5)
Net Carrying Amount	$ 4.2	$ 2.0
Minimum | Customer relationships and contracts
Intangible Assets [Line Items]
Useful Life (Years)	3 years	3 years
Minimum | Internally developed software
Intangible Assets [Line Items]
Useful Life (Years)	3 years	3 years
Minimum | Other
Intangible Assets [Line Items]
Useful Life (Years)	1 year	1 year
Maximum | Customer relationships and contracts
Intangible Assets [Line Items]
Useful Life (Years)	14 years	14 years
Maximum | Internally developed software
Intangible Assets [Line Items]
Useful Life (Years)	5 years	5 years
Maximum | Other
Intangible Assets [Line Items]
Useful Life (Years)	10 years	10 years

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6473545&loc=d3e61844-108004

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
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