Goodwill and Other Intangible Assets - Changes in Goodwill by Reportable Segment (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($)
Goodwill [Roll Forward]
Balance, January 1, 2016	$ 1,257.4
Goodwill acquired	23.9
Currency and other impacts	2.8
Balance, September 30, 2016	1,284.1
Right Management
Goodwill [Roll Forward]
Balance, January 1, 2016	62.1
Balance, September 30, 2016	62.1
Reportable segments | Americas
Goodwill [Roll Forward]
Balance, January 1, 2016	515.7
Goodwill acquired	0.0
Currency and other impacts	1.7
Balance, September 30, 2016	517.4
Reportable segments | Americas | United States | Reportable subsegments
Goodwill [Roll Forward]
Balance, January 1, 2016	476.9
Balance, September 30, 2016	476.5
Reportable segments | Southern Europe
Goodwill [Roll Forward]
Balance, January 1, 2016	97.2
Goodwill acquired	0.0
Currency and other impacts	6.1
Balance, September 30, 2016	103.3
Reportable segments | Southern Europe | France | Reportable subsegments
Goodwill [Roll Forward]
Balance, January 1, 2016	69.0
Balance, September 30, 2016	71.4
Reportable segments | Southern Europe | Italy | Reportable subsegments
Goodwill [Roll Forward]
Balance, January 1, 2016	4.5
Balance, September 30, 2016	4.7
Reportable segments | Northern Europe
Goodwill [Roll Forward]
Balance, January 1, 2016	441.9
Goodwill acquired	21.5
Currency and other impacts	(10.8)
Balance, September 30, 2016	452.6
Reportable segments | APME
Goodwill [Roll Forward]
Balance, January 1, 2016	75.6
Goodwill acquired	1.8
Currency and other impacts	5.8
Balance, September 30, 2016	83.2
Reportable segments | Right Management
Goodwill [Roll Forward]
Balance, January 1, 2016	62.1
Goodwill acquired	0.0
Currency and other impacts	0.0
Balance, September 30, 2016	62.1
Corporate
Goodwill [Roll Forward]
Balance, January 1, 2016	64.9
Goodwill acquired	0.6
Currency and other impacts	0.0
Balance, September 30, 2016	65.5
Corporate | Jefferson Wells
Goodwill [Roll Forward]
Balance, September 30, 2016	$ 55.5