Goodwill and Intangible Assets - Gross Carrying Amount and Accumulated Amortization of Intangible Assets (Detail) - USD ($) $ in Millions	Jul. 03, 2015	Sep. 26, 2014
Finite Lived Intangible Assets [Line Items]
Accumulated amortization	$ (61.6)	$ (56.9)
Net carrying amount subject to amortization	40.5	38.9
Acquired existing technology
Finite Lived Intangible Assets [Line Items]
Finite lived intangible assets, gross	58.1	54.6
Patents, licenses and other
Finite Lived Intangible Assets [Line Items]
Finite lived intangible assets, gross	29.1	28.8
Customer contracts and supplier relationship
Finite Lived Intangible Assets [Line Items]
Finite lived intangible assets, gross	$ 14.9	$ 12.4