Income Taxes - Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 24, 2016	Sep. 26, 2015
Deferred tax assets
Net operating loss carryforwards	$ 40.0	$ 45.4
Capital losses	19.1	25.7
Non-deductible accruals	21.1	16.3
Non-deductible reserves	31.1	26.8
Stock-based compensation	34.8	24.3
Research and other credits	10.7	14.5
Nonqualified deferred compensation plan	14.1	11.3
Other temporary differences	9.2	10.2
Deferred tax assets, gross	180.1	174.5
Less: valuation allowance	(46.2)	(60.9)
Deferred tax assets, net	133.9	113.6
Deferred tax liabilities
Depreciation and amortization	(1,030.8)	(1,171.5)
Debt discounts and deferrals	(75.1)	(100.1)
Deferred Tax Liabilities, Deferred Expense, Deferred Financing Costs	1.3	1.4
Deferred tax liabilities, net	(1,107.2)	(1,273.0)
Net deferred tax liabilities	$ (973.3)	$ (1,159.4)