EMPLOYEE STOCK PLANS - Net Share-Based Compensation Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 28, 2018	Dec. 29, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 10.5	$ 10.7
Income tax benefit for share-based compensation	(2.3)	(2.1)
Cost of revenues - Product
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	0.7	0.7
Cost of revenues - Service
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	1.1	1.0
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	1.1	1.2
Selling, general and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 7.6	$ 7.8