FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Jun. 29, 2018	Sep. 29, 2017
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents	$ 155.8
Available-for-sale securities	10.9	$ 60.1
APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	6.3
GPTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	4.6	4.4
DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		8.3
Fair Value, Measurements, Recurring
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	166.7	60.1
Contingent consideration	(3.0)
Total liabilities measured at fair value	(3.0)
Fair Value, Measurements, Recurring | APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	6.3
Fair Value, Measurements, Recurring | GPTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	4.6	4.4
Fair Value, Measurements, Recurring | Original CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		47.4
Fair Value, Measurements, Recurring | DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		8.3
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	155.8	0.0
Contingent consideration	0.0
Total liabilities measured at fair value	0.0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments | APTC Securities
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 | GPTC Securities
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 | Original CPTC loans
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 | DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	10.9	12.7
Contingent consideration	0.0
Total liabilities measured at fair value	0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs | APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	6.3
Fair Value, Measurements, Recurring | Significant Other Observable Inputs | GPTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	4.6	4.4
Fair Value, Measurements, Recurring | Significant Other Observable Inputs | Original CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs | DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		8.3
Fair Value, Measurements, Recurring | Significant Unobservable Inputs
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0.0	47.4
Contingent consideration	(3.0)
Total liabilities measured at fair value	(3.0)
Fair Value, Measurements, Recurring | Significant Unobservable Inputs | APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs | GPTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0	0.0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs | Original CPTC loans
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		47.4
Fair Value, Measurements, Recurring | Significant Unobservable Inputs | DRTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities		$ 0.0
Money Market Funds
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents	155.8
Money Market Funds | Fair Value, Measurements, Recurring
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents	155.8
Money Market Funds | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents	155.8
Money Market Funds | Fair Value, Measurements, Recurring | Significant Other Observable Inputs
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents	0.0
Money Market Funds | Fair Value, Measurements, Recurring | Significant Unobservable Inputs
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents	$ 0.0