Restructuring and Severance Charges - Restructuring Activities and Accrued Liabilities in the Consolidated Balance Sheets (Detail) $ in Millions	12 Months Ended
	Oct. 01, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 4.2
Ending Balance	3.5
Other Associated Costs
Restructuring Cost and Reserve [Line Items]
Provisions	(1.9)
Other Facilities
Restructuring Cost and Reserve [Line Items]
Beginning Balance	7.5
Provisions	(23.6)
Reversal of prior provision	(0.4)
Cash expenditures	(12.2)
Other non-cash settlement	0.1
Ending Balance	18.6
Other Facilities | Employee Severance
Restructuring Cost and Reserve [Line Items]
Beginning Balance	2.5
Provisions	(15.0)
Reversal of prior provision	(0.3)
Cash expenditures	(8.6)
Other non-cash settlement	(0.1)
Ending Balance	8.5
Other Facilities | Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance	4.6
Provisions	(6.7)
Reversal of prior provision	(0.1)
Cash expenditures	(3.2)
Other non-cash settlement	0.4
Ending Balance	8.4
Other Facilities | Other Associated Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance	0.4
Provisions	(1.9)
Reversal of prior provision	0.0
Cash expenditures	(0.4)
Other non-cash settlement	(0.2)
Ending Balance	$ 1.7