Income Taxes - Reconciliation of Income Tax Computed at the Federal Statutory Rate to Actual Tax Expenses (Detail) - USD ($) $ in Millions	12 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Sep. 27, 2015
Income Tax Disclosure [Abstract]
Tax computed at federal statutory rate	$ 47.6	$ (8.9)	$ 33.9
State taxes, net of federal impact	0.5	0.5	(2.1)
Foreign income taxed at different rates	(78.5)	(7.0)	(33.1)
Tax credits and incentives	(8.8)	(10.7)	(5.1)
Stock award compensation	(13.9)	(4.6)	1.3
Unrecognized tax benefits	11.4	30.6	3.7
Sale/transfer of assets	5.6	(45.6)	0.0
U.S. tax on foreign income	54.7	2.0	1.3
Non-deductible permanent items	0.0	6.2	0.9
Expiration of tax attributes	20.0	5.0	0.0
Investment in foreign subsidiaries	(0.2)	2.7	(0.5)
Withholding taxes	0.0	1.1	(0.3)
Foreign income tax rate changes	(4.0)	0.0	0.0
Other differences, net	2.6	0.6	(1.0)
Valuation allowance	(77.2)	35.3	13.3
Income Tax Expense (Benefit)	$ (40.2)	$ 7.2	$ 12.3