Goodwill and Other Intangible Assets - Changes in Goodwill by Reportable Segment (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Goodwill [Roll Forward]
Balance, January 1, 2017	$ 1,239.9
Goodwill acquired	7.3
Currency and other impacts	9.1
Balance, March 31, 2017	1,256.3
Right Management
Goodwill [Roll Forward]
Balance, January 1, 2017	62.1
Balance, March 31, 2017	62.1
Reportable segments | Americas
Goodwill [Roll Forward]
Balance, January 1, 2017	516.4
Goodwill acquired	0.0
Currency and other impacts	0.4
Balance, March 31, 2017	516.8
Reportable segments | Americas | United States | Reportable Subsegments
Goodwill [Roll Forward]
Balance, January 1, 2017	476.5
Balance, March 31, 2017	476.5
Reportable segments | Southern Europe
Goodwill [Roll Forward]
Balance, January 1, 2017	97.0
Goodwill acquired	7.2
Currency and other impacts	1.8
Balance, March 31, 2017	106.0
Reportable segments | Southern Europe | France | Reportable Subsegments
Goodwill [Roll Forward]
Balance, January 1, 2017	66.8
Balance, March 31, 2017	67.7
Reportable segments | Southern Europe | Italy | Reportable Subsegments
Goodwill [Roll Forward]
Balance, January 1, 2017	4.4
Balance, March 31, 2017	4.4
Reportable segments | Northern Europe
Goodwill [Roll Forward]
Balance, January 1, 2017	421.9
Goodwill acquired	0.1
Currency and other impacts	3.5
Balance, March 31, 2017	425.5
Reportable segments | APME
Goodwill [Roll Forward]
Balance, January 1, 2017	77.0
Goodwill acquired	0.0
Currency and other impacts	3.4
Balance, March 31, 2017	80.4
Reportable segments | Right Management
Goodwill [Roll Forward]
Balance, January 1, 2017	62.1
Goodwill acquired	0.0
Currency and other impacts	0.0
Balance, March 31, 2017	62.1
Corporate
Goodwill [Roll Forward]
Balance, January 1, 2017	65.5
Goodwill acquired	0.0
Currency and other impacts	0.0
Balance, March 31, 2017	65.5
Corporate | Jefferson Wells
Goodwill [Roll Forward]
Balance, March 31, 2017	$ 55.5