Schedule of Accumulated Other Comprehensive Income (Loss) Expected to be Recognized as Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 26, 2014
Defined Benefit Plan Disclosure [Line Items]
Prior service credit (cost)	$ 0.3
Net gain (loss)	(2.4)
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year, Total	(2.1)
Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Prior service credit (cost)	(0.2)
Net gain (loss)	(2.4)
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year, Total	(2.6)
Post-Retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Prior service credit (cost)	0.5
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year, Total	$ 0.5