Restructuring Costs (Details)	6 Months Ended
	Jun. 30, 2017 USD ($)
Restructuring Cost [Abstract]
Net restructuring costs	$ 34,500,000
Restructuring reserve [Roll Forward]
Balance, beginning of period	4,500,000
Costs paid or utilized	(9,500,000)
Severance Costs	24,700,000
Office closure costs and other	9,800,000
Balance, end of period	29,500,000
Reportable segments | Americas
Restructuring reserve [Roll Forward]
Balance, beginning of period	400,000
Costs paid or utilized	(500,000)
Severance Costs	5,800,000
Office closure costs and other	500,000
Balance, end of period	6,200,000
Reportable segments | Americas | United States | Reportable subsegments
Restructuring reserve [Roll Forward]
Balance, beginning of period	400,000
Balance, end of period	4,200,000
Reportable segments | Southern Europe
Restructuring reserve [Roll Forward]
Balance, beginning of period	1,300,000
Costs paid or utilized	0
Severance Costs	0
Office closure costs and other	0
Balance, end of period	1,300,000
Reportable segments | Southern Europe | France | Reportable subsegments
Restructuring reserve [Roll Forward]
Balance, beginning of period	1,300,000
Balance, end of period	1,300,000
Reportable segments | Southern Europe | Italy | Reportable subsegments
Restructuring reserve [Roll Forward]
Balance, beginning of period	0
Balance, end of period	0
Reportable segments | Northern Europe
Restructuring reserve [Roll Forward]
Balance, beginning of period	2,600,000
Costs paid or utilized	(7,900,000)
Severance Costs	15,600,000
Office closure costs and other	8,200,000
Balance, end of period	18,500,000
Reportable segments | APME
Restructuring reserve [Roll Forward]
Balance, beginning of period	100,000
Costs paid or utilized	(1,000,000)
Severance Costs	900,000
Office closure costs and other	500,000
Balance, end of period	500,000
Reportable segments | Right Management
Restructuring reserve [Roll Forward]
Balance, beginning of period	100,000
Costs paid or utilized	0
Severance Costs	1,400,000
Office closure costs and other	600,000
Balance, end of period	2,100,000
Corporate
Restructuring reserve [Roll Forward]
Balance, beginning of period	0
Costs paid or utilized	(100,000)
Severance Costs	1,000,000
Office closure costs and other	0
Balance, end of period	$ 900,000