Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale corporate debt security	$ 75.6	$ 62.7
Option to purchase a privately-held company		1.4
Derivative assets	1.5
Total assets measured at fair value	77.1	114.1
Derivative liabilities		(1.1)
Contingent consideration	(7.5)	(2.5)
Total liabilities measured at fair value	(7.5)	(3.6)
Money Market Funds
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Money market funds		50.0
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value		50.0
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Money Market Funds
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Money market funds		50.0
Significant Other Observable Inputs (Level 2)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Derivative assets	1.5
Total assets measured at fair value	1.5
Derivative liabilities		(1.1)
Total liabilities measured at fair value		(1.1)
Significant Unobservable Inputs (Level 3)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale corporate debt security	75.6	62.7
Option to purchase a privately-held company		1.4
Total assets measured at fair value	75.6	64.1
Contingent consideration	(7.5)	(2.5)
Total liabilities measured at fair value	$ (7.5)	$ (2.5)