Segments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Revenues [Abstract]
Total net revenues	$ 1,319.6	$ 1,248.6	$ 1,222.2	$ 1,067.4	$ 1,101.6	$ 1,125.9	$ 1,229.5	$ 1,170.1	$ 4,857.8	$ 4,627.1	$ 4,669.1
Routing [Member]
Net Revenues [Abstract]
Total net revenues									2,359.2	2,223.9	2,318.0
Switching [Member]
Net Revenues [Abstract]
Total net revenues									768.3	721.2	638.0
Security [Member]
Net Revenues [Abstract]
Total net revenues									435.6	463.6	563.9
Total product [Member]
Net Revenues [Abstract]
Total net revenues									3,563.1	3,408.7	3,519.9
Total service [Member]
Net Revenues [Abstract]
Total net revenues									$ 1,294.7	$ 1,218.4	$ 1,149.2