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 | ||||||