Income Taxes - Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($)	Sep. 26, 2020	Sep. 28, 2019
Deferred tax assets
Net operating loss carryforwards	$ 81,100,000	$ 34,500,000
Capital losses	57,000,000.0	6,400,000
Non-deductible accruals	24,900,000	24,700,000
Non-deductible reserves	33,200,000	22,700,000
UK Intangible assets	0	25,400,000
Stock-based compensation	18,600,000	20,900,000
Tax credits	10,200,000	14,800,000
Nonqualified deferred compensation plan	14,400,000	12,900,000
Deferred tax assets lease liability	17,300,000	0
Other temporary differences	25,200,000	17,800,000
Deferred tax assets, gross	281,900,000	180,100,000
Less: valuation allowance	(118,500,000)	(60,700,000)
Deferred tax assets, net	163,400,000	119,400,000
Deferred tax liabilities
Depreciation and amortization	(333,900,000)	(373,000,000.0)
Right of use asset	(15,800,000)	0
Debt discounts and deferrals	0	(4,500,000)
Deferred tax liabilities, net	(349,700,000)	(377,500,000)
Net deferred tax liabilities	$ (186,300,000)	$ (258,100,000)