Employee Stock Plans - Stock-Based Compensation Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		$ 3.1	$ 2.9	$ 6.2	$ 5.8
Income tax benefit		(0.6)	(3.1)	(1.5)	(4.6)
Stock-based compensation expense, net of tax		2.5	(0.2)	4.7	1.2
Cost of Revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	[1]	0.5	0.6	1.0	1.2
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		0.1	0.1	0.1	0.2
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		0.3	0.3	0.6	0.6
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		$ 2.2	$ 1.9	$ 4.5	$ 3.8

[1] Stock-based compensation expense capitalized in inventory for the three and six months ended June 26, 2020 and for the three and six months ended June 28, 2019 was not significant.