Stock-Based Compensation - Stock-Based Compensation Expense in Consolidated Statements of Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 29, 2025	Mar. 30, 2024	Mar. 29, 2025	Mar. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 28.4	$ 25.8	$ 58.5	$ 54.5
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	3.3	3.2	6.8	5.9
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2.5	3.0	5.0	6.2
Selling and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	4.0	3.6	7.7	6.9
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 18.6	$ 16.0	$ 39.0	$ 35.5