Goodwill and Other Intangible Assets - Goodwill by Reporting Unit (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 1,284.1	$ 1,257.4
United States
Goodwill [Line Items]
Goodwill	532.0	532.4
Germany
Goodwill [Line Items]
Goodwill	130.7	127.1
Netherlands
Goodwill [Line Items]
Goodwill	118.4	98.7
United Kingdom
Goodwill [Line Items]
Goodwill	89.6	101.1
France
Goodwill [Line Items]
Goodwill	71.4	69.0
Right Management
Goodwill [Line Items]
Goodwill	62.1	62.1
Other reporting units
Goodwill [Line Items]
Goodwill	$ 279.9	$ 267.0