Segments (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($) Customer	Dec. 31, 2014 USD ($) Customer
Net Revenues [Abstract]
Total net revenues	$ 1,385.6	$ 1,285.3	$ 1,221.3	$ 1,097.9	$ 1,319.6	$ 1,248.6	$ 1,222.2	$ 1,067.4	$ 4,990.1	$ 4,857.8	$ 4,627.1
Number of customers accounting for more than 10% of revenues | Customer									0	0	0
Routing [Member]
Net Revenues [Abstract]
Total net revenues									$ 2,352.9	$ 2,359.2	$ 2,223.9
Switching [Member]
Net Revenues [Abstract]
Total net revenues									858.0	768.3	721.2
Security [Member]
Net Revenues [Abstract]
Total net revenues									318.0	435.6	463.6
Total product [Member]
Net Revenues [Abstract]
Total net revenues									3,528.9	3,563.1	3,408.7
Total service [Member]
Net Revenues [Abstract]
Total net revenues									$ 1,461.2	$ 1,294.7	$ 1,218.4