Gross Carrying Amount and Accumulated Amortization of Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Finite Lived Intangible Assets [Line Items]
Accumulated amortization	$ (56.9)	$ (53.1)
Net carrying amount	38.9	23.4
Acquired existing technology
Finite Lived Intangible Assets [Line Items]
Finite Lived Intangible Assets Gross	54.6	36.6
Patents Licenses And Other
Finite Lived Intangible Assets [Line Items]
Finite Lived Intangible Assets Gross	28.8	29.0
Customer Contracts And Relationships
Finite Lived Intangible Assets [Line Items]
Finite Lived Intangible Assets Gross	$ 12.4	$ 10.9