Goodwill and Other Intangible Assets - Goodwill by Reporting Unit (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 1,256.3	$ 1,239.9
United States
Goodwill [Line Items]
Goodwill	532.0	532.0
Germany
Goodwill [Line Items]
Goodwill	120.6	121.4
Netherlands
Goodwill [Line Items]
Goodwill	112.3	110.9
United Kingdom
Goodwill [Line Items]
Goodwill	82.8	81.4
France
Goodwill [Line Items]
Goodwill	67.7	66.8
Right Management
Goodwill [Line Items]
Goodwill	62.1	62.1
Other reporting units
Goodwill [Line Items]
Goodwill	$ 278.8	$ 265.3