Segments - Geographical (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Revenues by Geographic Region [Line Items]
Net revenues:	$ 1,222.6	$ 1,138.2	$ 1,086.3	$ 998.0	$ 1,208.1	$ 1,133.1	$ 1,102.5	$ 1,001.7	$ 4,445.1	$ 4,445.4	$ 4,647.5
Property and equipment, net and purchased intangible assets, net	1,029.0				1,016.7				1,029.0	1,016.7
Total Americas
Net Revenues by Geographic Region [Line Items]
Net revenues:									2,445.1	2,518.0	2,541.2
United States
Net Revenues by Geographic Region [Line Items]
Net revenues:									2,233.9	2,299.8	2,339.1
Property and equipment, net and purchased intangible assets, net	807.4				815.9				807.4	815.9
Other
Net Revenues by Geographic Region [Line Items]
Net revenues:									211.2	218.2	202.1
Europe, Middle East, and Africa
Net Revenues by Geographic Region [Line Items]
Net revenues:									1,233.8	1,215.3	1,290.8
Asia Pacific
Net Revenues by Geographic Region [Line Items]
Net revenues:									766.2	712.1	$ 815.5
International
Net Revenues by Geographic Region [Line Items]
Property and equipment, net and purchased intangible assets, net	$ 221.6				$ 200.8				$ 221.6	$ 200.8