Share-Based Compensation Plans - Effects of Stock-Based Compensation Expense Related to Stock-Based Awards to Employees and Non-Employees (Detail) - USD ($) $ in Thousands	12 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 35,674	$ 23,792	$ 31,937
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	3,609	2,936	3,869
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	12,794	8,551	13,448
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 19,271	$ 12,305	$ 14,620