Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Jul. 03, 2015	Sep. 26, 2014
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	$ 90.9	$ 75.6
Derivative assets	1.0	1.5
Corporate debt securities: CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	81.9	75.6
Corporate debt securities: Other
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.4
Non-U.S. government security
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.6
Fair Value, Measurements, Recurring
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Derivative assets	1.0	1.5
Total assets measured at fair value	91.9	77.1
Contingent consideration	(4.1)	(7.5)
Total liabilities measured at fair value	(4.1)	(7.5)
Fair Value, Measurements, Recurring | Corporate debt securities: CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	81.9	75.6
Fair Value, Measurements, Recurring | Corporate debt securities: Other
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.4
Fair Value, Measurements, Recurring | Non-U.S. government security
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.6
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Derivative assets	0.0	0.0
Total assets measured at fair value	0.0	0.0
Contingent consideration	0.0	0.0
Total liabilities measured at fair value	0.0	0.0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments (Level 1) | Corporate debt securities: CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0	0.0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments (Level 1) | Corporate debt securities: Other
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments (Level 1) | Non-U.S. government security
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Derivative assets	1.0	1.5
Total assets measured at fair value	10.0	1.5
Contingent consideration	0.0	0.0
Total liabilities measured at fair value	0.0	0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities: CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0	0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities: Other
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.4
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Non-U.S. government security
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.6
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Derivative assets	0.0	0.0
Total assets measured at fair value	81.9	75.6
Contingent consideration	(4.1)	(7.5)
Total liabilities measured at fair value	(4.1)	(7.5)
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities: CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	81.9	$ 75.6
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities: Other
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Non-U.S. government security
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	$ 0.0