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Segment Reporting (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Revenue and Long-Lived Assets and Goodwill by Geographic Region |  |  |  |  |  |  |  |  |  |  |
Revenue | $ 4,176.6 | $ 3,719.5 | $ 3,790.1 | $ 3,587.4 | $ 4,241.8 | $ 3,791.1 | $ 3,884.9 | $ 3,499.1 | $ 15,273.6 | $ 15,416.9 | $ 15,134.4
Americas |  |  |  |  |  |  |  |  |  |  |
Revenue and Long-Lived Assets and Goodwill by Geographic Region |  |  |  |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  |  | 9,180.8 | 9,597.6 | 9,359.0
Long-lived assets and goodwill | 6,633.8 |  |  |  | 6,662.7 |  |  |  | 6,633.8 | 6,662.7 | 6,103.4
United States |  |  |  |  |  |  |  |  |  |  |
Revenue and Long-Lived Assets and Goodwill by Geographic Region |  |  |  |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  |  | 8,196.9 | 8,627.8 | 8,526.7
EMEA |  |  |  |  |  |  |  |  |  |  |
Revenue and Long-Lived Assets and Goodwill by Geographic Region |  |  |  |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  |  | 4,442.5 | 4,183.1 | 4,203.5
Long-lived assets and goodwill | 2,840.8 |  |  |  | 2,469.1 |  |  |  | 2,840.8 | 2,469.1 | 2,737.8
Asia Pacific |  |  |  |  |  |  |  |  |  |  |
Revenue and Long-Lived Assets and Goodwill by Geographic Region |  |  |  |  |  |  |  |  |  |  |
Revenue |  |  |  |  |  |  |  |  | 1,650.3 | 1,636.2 | 1,571.9
Long-lived assets and goodwill | $ 553.8 |  |  |  | $ 519.1 |  |  |  | $ 553.8 | $ 519.1 | $ 527.9

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