Employee Stock Plans - Stock-Based Compensation Expense Included in Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 27, 2019	Dec. 28, 2018	Dec. 29, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		$ 12.1	$ 10.3	$ 7.8
Income tax benefit			(3.0)	(0.9)
Net stock-based compensation expense		12.1	7.3	6.9
Cost of Revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	[1]	2.4	2.1	1.5
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		1.3	1.0	0.6
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		0.3	0.1	0.2
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation		$ 8.1	$ 7.1	$ 5.5

[1] Stock-based compensation expenses capitalized in inventory for fiscal years 2019, 2018 and 2017 were considered immaterial.