Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenue	$ 3,706.6	$ 3,749.6	$ 10,981.1	$ 11,122.7
Americas
Revenue	2,292.0	2,224.4	6,807.1	6,600.9
Long-lived assets and goodwill	6,107.8	6,103.9	6,107.8	6,103.9
UNITED STATES
Revenue	2,098.5	2,004.3	6,203.0	5,937.4
EMEA
Revenue	1,027.8	1,119.5	3,035.9	3,355.1
Long-lived assets and goodwill	2,750.4	2,902.1	2,750.4	2,902.1
Asia Pacific
Revenue	386.8	405.7	1,138.1	1,166.7
Long-lived assets and goodwill	$ 515.8	$ 582.8	$ 515.8	$ 582.8