Goodwill and Other Intangible Assets - Schedule of Goodwill by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Beginning balance	$ 2,479.6	$ 2,455.0
Foreign currency translation	(16.8)	24.6
Ending balance	2,462.8	2,479.6
Corporate
Goodwill [Roll Forward]
Beginning balance	1,074.1	1,074.1
Foreign currency translation	0.0	0.0
Ending balance	1,074.1	1,074.1
Accumulated impairment losses	1,571.0
Small Business
Goodwill [Roll Forward]
Beginning balance	185.9	185.9
Foreign currency translation	0.0	0.0
Ending balance	185.9	185.9
Public
Goodwill [Roll Forward]
Beginning balance	929.6	929.6
Foreign currency translation	0.0	0.0
Ending balance	929.6	929.6
Accumulated impairment losses	354.0
Other
Goodwill [Roll Forward]
Beginning balance	290.0	265.4
Foreign currency translation	(16.8)	24.6
Ending balance	273.2	$ 290.0
Accumulated impairment losses	$ 28.0