Employee Stock Plans - Summary the Effect of Recording Pre-Tax Share-Based Compensation Expense for Equity Incentive Awards (Detail) - USD ($) $ in Millions	12 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 43.9	$ 47.9	$ 46.4
Restricted Stock Units (RSUs)
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	26.1	21.1	21.6
Performance units and performance options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	2.1	13.6	12.1
Stock options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	8.9	8.6	8.5
Employee Stock Purchase Plans
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	5.9	4.5	4.2
Cash-settled stock appreciation rights
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 0.9	$ 0.1	$ 0.0