Segments - Geographic (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total net revenues	$ 1,179.8	$ 1,257.8	$ 3,466.5	$ 3,787.7
Total Americas
Segment Reporting Information [Line Items]
Total net revenues	643.1	729.2	1,906.4	2,241.6
United States
Segment Reporting Information [Line Items]
Total net revenues	597.1	668.8	1,754.2	2,076.0
Other
Segment Reporting Information [Line Items]
Total net revenues	46.0	60.4	152.2	165.6
Europe, Middle East, and Africa
Segment Reporting Information [Line Items]
Total net revenues	329.9	298.6	946.8	871.3
Asia Pacific
Segment Reporting Information [Line Items]
Total net revenues	$ 206.8	$ 230.0	$ 613.3	$ 674.8