Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	$ 3,629.6	$ 3,587.4
Americas
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	2,094.1	2,245.9
Long-lived assets and goodwill	6,838.3	6,673.8
United States
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	1,881.0	2,011.7
EMEA
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	1,143.5	966.5
Long-lived assets and goodwill	2,941.3	2,544.3
Asia Pacific
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	392.0	375.0
Long-lived assets and goodwill	$ 547.5	$ 535.3