Operating Segments - Reconciliation of Total Reportable Segments' Revenues and EBITDA to Consolidated Revenues and Consolidated Income from Continuing Operations Before Taxes (Parenthetical) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 27, 2015	Sep. 28, 2014
Tripwire [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Compensation expense	$ 9.2
Cost of sales related to adjustment of acquired inventory	$ 0.3
Grass Valley and Prosoft [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Cost of sales related to adjustment of acquired inventory		$ 8.3