Other Financial Information, Other Long Term Assets (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	18 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Apr. 01, 2017	Dec. 31, 2014	Oct. 01, 2014
Other Financial Information [Line Items]
Privately-held investments	$ 91.3	$ 91.3		$ 89.9
Licensed software	7.7	7.7		8.6
Federal income tax receivable	28.9	28.9		20.0
Customer financing receivable	1.5	1.5		16.9
Inventory	8.7	8.7		8.0
Prepaid costs, deposits, and other	60.5	60.5		35.5
Promissory note in connection with the sale of Junos Pulse	125.0	125.0		125.0
Interest Receivable	6.3	6.3		0.0
Other long-term assets	329.9	329.9		$ 303.9
Scheduled interest payments not received	3.1	3.1
Interest income	$ 1.6	$ 4.7
Junos Pulse [Member]
Other Financial Information [Line Items]
Promissory note in connection with the sale of Junos Pulse					$ 125.0
Consideration					230.7
Cash Consideration					105.7
Working capital adjustment					$ 19.3
Junos Pulse [Member] | Scenario, Forecast [Member] | Subsequent Event [Member]
Other Financial Information [Line Items]
Required minimum payment due on notes receivable			$ 75.0