Employee Stock Plans - Net Share-Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Apr. 03, 2015	Mar. 28, 2014	Apr. 03, 2015	Mar. 28, 2014
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 12,501	$ 9,596	$ 25,238	$ 18,640
Income tax benefit for share-based compensation	(3,943)	(2,939)	(7,916)	(5,737)
Cost of revenues - Product
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	1,206	717	2,315	1,424
Cost of revenues - Service
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	986	1,115	1,938	2,062
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	1,654	1,320	3,392	2,621
Selling, general and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 8,655	$ 6,444	$ 17,593	$ 12,533