Income Taxes - Components of Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 27, 2015	Sep. 28, 2014	Sep. 29, 2013
Income Tax Disclosure [Abstract]
Accounts receivable, net	$ 1.9	$ 1.2
Inventories	17.5	14.5
Accrued employee benefit expenses	8.4	8.8
Net operating losses	164.6	149.6
Tax credits	153.5	144.2
Accrued other expenses	9.7	11.4
Deferred equity compensation	18.9	16.7
Property and equipment, net	(13.8)	(3.1)
Other assets	11.4	11.8
Total deferred tax assets	399.7	361.3
Intangible assets	(137.1)	(127.2)
Deferred Tax Liabilities, Foreign Declared Dividend	0.0	(3.6)
Effective Income Tax Reconciliation, Deduction, Foreign Declared Dividends, Amount	(0.5)	3.6	$ 0.0
Total deferred tax liabilities	(137.1)	(130.8)
Less valuation allowance	(250.6)	(218.9)
Deferred Tax Assets (Liabilities), Net, Total	$ 12.0	$ 11.6