Segments - Geographical (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($) Customer	Dec. 31, 2017 USD ($) Customer
Net Revenues by Geographic Region [Line Items]
Net revenues	$ 1,208.1	$ 1,133.1	$ 1,102.5	$ 1,001.7	$ 1,181.0	$ 1,179.8	$ 1,204.1	$ 1,082.6	$ 4,445.4	$ 4,647.5	$ 5,027.2
Property and equipment, net and purchased intangible assets, net	1,016.7				1,070.2				$ 1,016.7	$ 1,070.2
Number of customers accounting for more than 10% of revenues | Customer									0	0	0
Total Americas
Net Revenues by Geographic Region [Line Items]
Net revenues									$ 2,518.0	$ 2,541.2	$ 2,947.2
United States
Net Revenues by Geographic Region [Line Items]
Net revenues									2,299.8	2,339.1	2,712.6
Property and equipment, net and purchased intangible assets, net	815.9				941.7				815.9	941.7
Other
Net Revenues by Geographic Region [Line Items]
Net revenues									218.2	202.1	234.6
Europe, Middle East, and Africa
Net Revenues by Geographic Region [Line Items]
Net revenues									1,215.3	1,290.8	1,195.8
Asia Pacific
Net Revenues by Geographic Region [Line Items]
Net revenues									712.1	815.5	$ 884.2
International
Net Revenues by Geographic Region [Line Items]
Property and equipment, net and purchased intangible assets, net	$ 200.8				$ 128.5				$ 200.8	$ 128.5