Goodwill and Other Intangible Assets - Changes in the Carrying Amount of Goodwill by Reportable Segment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Goodwill gross balance	$ 1,361.8	$ 1,361.0	$ 1,361.5
Accumulated asset impairments	(515.7)	(515.7)	(515.7)
Foreign currency impact	0.8	(0.5)
Goodwill	846.1	845.3	845.8
Americas
Goodwill
Goodwill gross balance	1,144.8	1,144.8	1,144.8
Accumulated asset impairments	(312.2)	(312.2)	(312.2)
Foreign currency impact	0.0	0.0
Goodwill	832.6	832.6	832.6
EMEA
Goodwill
Goodwill gross balance	208.4	208.2	208.3
Accumulated asset impairments	(203.5)	(203.5)	(203.5)
Foreign currency impact	0.2	(0.1)
Goodwill	4.9	4.7	4.8
APAC
Goodwill
Goodwill gross balance	8.6	8.0	8.4
Accumulated asset impairments	0.0	0.0	0.0
Foreign currency impact	0.6	(0.4)
Goodwill	$ 8.6	$ 8.0	$ 8.4

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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