Segments - Revenue by Product (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			1
Total net revenues	$ 1,086.3	$ 1,102.5	$ 2,084.3	$ 2,104.2
Product
Segment Reporting Information [Line Items]
Total net revenues	692.3	713.9	1,301.1	1,332.6
Routing
Segment Reporting Information [Line Items]
Total net revenues	403.2	416.9	717.7	791.6
Switching
Segment Reporting Information [Line Items]
Total net revenues	208.8	215.6	428.6	392.0
Security
Segment Reporting Information [Line Items]
Total net revenues	80.3	81.4	154.8	149.0
Service
Segment Reporting Information [Line Items]
Total net revenues	$ 394.0	$ 388.6	$ 783.2	$ 771.6