Income Taxes - Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 28, 2019	Sep. 29, 2018
Deferred tax assets
Net operating loss carryforwards	$ 34.5	$ 30.9
Capital losses	6.4	6.5
Non-deductible accruals	24.7	30.7
Non-deductible reserves	22.7	22.1
UK Intangible assets	25.4	0.0
Stock-based compensation	20.9	24.0
Research and other credits	14.8	13.3
Nonqualified deferred compensation plan	12.9	12.3
Other temporary differences	17.8	11.5
Deferred tax assets, gross	180.1	151.3
Less: valuation allowance	(60.7)	(25.5)
Deferred tax assets, net	119.4	125.8
Deferred tax liabilities
Depreciation and amortization	(373.0)	(606.6)
Debt discounts and deferrals	(4.5)	(4.5)
Deferred tax liabilities, net	(377.5)	(611.1)
Net deferred tax liabilities	$ (258.1)	$ (485.3)