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Goodwill and Other Intangible Assets - Intangible Assets by Asset Type (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Intangible Assets [Line Items] |  |
Gross Carrying Amount | $ 2,694.5 | $ 2,655.3
Accumulated Amortization | (1,797.5) | (1,599.7)
Net Carrying Amount | 897.0 | 1,055.6
Customer relationships and contracts |  |
Intangible Assets [Line Items] |  |
Gross Carrying Amount | 2,106.8 | 2,084.6
Accumulated Amortization | (1,490.8) | (1,322.7)
Net Carrying Amount | 616.0 | 761.9
Trade name |  |
Intangible Assets [Line Items] |  |
Gross Carrying Amount | 422.2 | 422.1
Accumulated Amortization | (216.3) | (195.2)
Net Carrying Amount | 205.9 | 226.9
Internally developed software |  |
Intangible Assets [Line Items] |  |
Gross Carrying Amount | 162.6 | 142.6
Accumulated Amortization | (89.6) | (77.7)
Net Carrying Amount | 73.0 | 64.9
Other |  |
Intangible Assets [Line Items] |  |
Gross Carrying Amount | 2.9 | 6.0
Accumulated Amortization | (0.8) | (4.1)
Net Carrying Amount | $ 2.1 | $ 1.9

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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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