Other Financial Information, Other Long Term Assets (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	18 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Apr. 01, 2017	Dec. 31, 2015	Oct. 01, 2014
Other Financial Information [Line Items]
Privately-held investments	$ 88.5	$ 88.5		$ 102.4
Licensed software	6.2	6.2		7.1
Federal income tax receivable	40.8	40.8		28.9
Inventory	5.6	5.6		8.4
Prepaid costs, deposits, and other	47.2	47.2		43.3
Deferred tax asset	13.2	13.2		55.9
Promissory note in connection with the sale of Junos Pulse	57.9	57.9		132.9
Other long-term assets	259.4	259.4		$ 378.9
Interest income	2.7	5.3
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]
Other Financial Information [Line Items]
Required minimum payment due on notes receivable			$ 75.0
Prepaid Expenses and Other Current Assets [Member] | Junos Pulse [Member]
Other Financial Information [Line Items]
Promissory note in connection with the sale of Junos Pulse	$ 75.0	$ 75.0