Segments (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) segment	Jun. 30, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			1
Total net revenues	$ 1,221.3	$ 1,222.2	$ 2,319.2	$ 2,289.6
Routing [Member]
Segment Reporting Information [Line Items]
Total net revenues	574.7	602.4	1,078.8	1,107.2
Switching [Member]
Segment Reporting Information [Line Items]
Total net revenues	209.2	190.2	384.7	356.7
Security [Member]
Segment Reporting Information [Line Items]
Total net revenues	78.2	107.1	151.6	199.9
Total product [Member]
Segment Reporting Information [Line Items]
Total net revenues	862.1	899.7	1,615.1	1,663.8
Total service [Member]
Segment Reporting Information [Line Items]
Total net revenues	$ 359.2	$ 322.5	$ 704.1	$ 625.8