Restructuring and Severance Charges - Restructuring Activities and Accrued Liabilities in the Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	12 Months Ended
	Oct. 02, 2016	Sep. 27, 2015
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 3.4
Ending Balance	4.2	$ 3.4
Employee Severance
Restructuring Cost and Reserve [Line Items]
Provisions	(55.4)
Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Provisions	(5.1)
Other Associated Costs
Restructuring Cost and Reserve [Line Items]
Provisions	(4.2)	(4.0)
Other Facilities
Restructuring Cost and Reserve [Line Items]
Beginning Balance	6.2
Provisions	(64.7)
Cash expenditures	(36.2)
Other non-cash settlement	(26.3)
Ending Balance	7.5	6.2
Other Facilities | Employee Severance
Restructuring Cost and Reserve [Line Items]
Beginning Balance	2.9
Cash expenditures	(32.4)
Other non-cash settlement	(22.9)
Ending Balance	2.5	2.9
Other Facilities | Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance	3.2
Cash expenditures	(2.9)
Other non-cash settlement	(0.5)
Ending Balance	4.6	3.2
Other Facilities | Other Associated Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance	0.1
Cash expenditures	(0.9)
Other non-cash settlement	(2.9)
Ending Balance	$ 0.4	$ 0.1