Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	$ 3,790.1	$ 3,884.9	$ 7,377.6	$ 7,384.0
Americas
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	2,296.8	2,428.6	4,542.7	4,627.1
Long-lived assets and goodwill	6,654.2	6,574.0	6,654.2	6,574.0
United States
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	2,060.9	2,190.5	4,072.6	4,198.0
EMEA
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	1,088.0	1,056.1	2,054.6	2,002.4
Long-lived assets and goodwill	2,678.0	2,644.9	2,678.0	2,644.9
Asia Pacific
Revenue and Long-Lived Assets and Goodwill by Geographic Region
Revenue	405.3	400.2	780.3	754.5
Long-lived assets and goodwill	$ 537.5	$ 532.9	$ 537.5	$ 532.9