Segments - Revenue by Product (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($) Reportable_Segment
Segment Reporting Information [Line Items]
Number of reportable segments	1	1
Total net revenues	$ 1,001.7	$ 1,082.6
Product
Segment Reporting Information [Line Items]
Total net revenues	618.7	710.8
Routing
Segment Reporting Information [Line Items]
Total net revenues	374.7	408.1
Switching
Segment Reporting Information [Line Items]
Total net revenues	176.4	230.0
Security
Segment Reporting Information [Line Items]
Total net revenues	67.6	72.7
Service
Segment Reporting Information [Line Items]
Total net revenues	$ 383.0	$ 371.8