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
	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 47.9	$ 46.4	$ 39.2
Restricted Stock Units (RSUs)
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	21.1	21.6	22.8
Performance units and performance options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	13.6	12.1	3.4
Stock options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	8.6	8.5	9.2
Employee Stock Purchase Plans
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	4.5	4.2	3.8
Cash-settled stock appreciation rights
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation expense	$ 0.1	$ 0.0	$ 0.0