Goodwill and Other Assets (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 1,396.6	$ 1,289.0	$ 452.2
Accumulated impairment losses	(290.7)	(290.7)	(290.7)
Beginning balance	998.3	161.5
Goodwill acquired	5.6	882.6
Goodwill adjustment	(2.9)	(0.5)
Currency translation adjustment	104.9	(45.3)
Ending balance	1,105.9	998.3
Services Segment [Member]
Goodwill [Line Items]
Goodwill	951.4	890.0	452.2
Accumulated impairment losses	(290.7)	(290.7)	(290.7)
Beginning balance	599.3	161.5
Goodwill acquired	5.6	459.1
Goodwill adjustment	(1.1)	(0.5)
Currency translation adjustment	56.9	(20.8)
Ending balance	660.7	599.3
Software Segment [Member]
Goodwill [Line Items]
Goodwill	251.0	224.9	0.0
Accumulated impairment losses	0.0	0.0	0.0
Beginning balance	224.9	0.0
Goodwill acquired	0.0	238.7
Goodwill adjustment	(1.0)	0.0
Currency translation adjustment	27.1	(13.8)
Ending balance	251.0	224.9
Systems Segment [Member]
Goodwill [Line Items]
Goodwill	194.2	174.1	0.0
Accumulated impairment losses	0.0	0.0	$ 0.0
Beginning balance	174.1	0.0
Goodwill acquired	0.0	184.8
Goodwill adjustment	(0.8)	0.0
Currency translation adjustment	20.9	(10.7)
Ending balance	$ 194.2	$ 174.1