Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue	$ 3,791.1	$ 3,706.6	$ 11,175.1	$ 10,981.1
Americas
Revenue	2,366.4	2,292.0	6,993.5	6,807.1
Long-lived assets and goodwill	6,577.0	6,107.8	6,577.0	6,107.8
UNITED STATES
Revenue	2,110.7	2,098.5	6,308.8	6,203.0
EMEA
Revenue	1,005.8	1,027.8	3,008.1	3,035.9
Long-lived assets and goodwill	2,606.7	2,750.4	2,606.7	2,750.4
Asia Pacific
Revenue	418.9	386.8	1,173.5	1,138.1
Long-lived assets and goodwill	$ 541.3	$ 515.8	$ 541.3	$ 515.8