FAIR VALUE - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 29, 2019	Sep. 28, 2018
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	$ 65.0	$ 62.5
Fair Value, Measurements, Recurring
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	69.0	106.6
Contingent consideration	(17.8)	(24.4)
Total liabilities measured at fair value	(17.8)	(24.4)
Fair Value, Measurements, Recurring | MPTC Series B-1 Bonds
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	26.1	25.1
Fair Value, Measurements, Recurring | MPTC Series B-2 Bonds (1)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	24.1	23.1
Fair Value, Measurements, Recurring | APTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	6.3	6.4
Fair Value, Measurements, Recurring | GPTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.5	7.9
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	4.0	44.1
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 | MPTC Series B-1 Bonds
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 | MPTC Series B-2 Bonds (1)
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 | APTC 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 | 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 Other Observable Inputs
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	65.0	62.5
Contingent consideration	0.0	0.0
Total liabilities measured at fair value	0.0	0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs | MPTC Series B-1 Bonds
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	26.1	25.1
Fair Value, Measurements, Recurring | Significant Other Observable Inputs | MPTC Series B-2 Bonds (1)
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	24.1	23.1
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	6.4
Fair Value, Measurements, Recurring | Significant Other Observable Inputs | GPTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	8.5	7.9
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	0.0
Contingent consideration	(17.8)	(24.4)
Total liabilities measured at fair value	(17.8)	(24.4)
Fair Value, Measurements, Recurring | Significant Unobservable Inputs | MPTC Series B-1 Bonds
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 | MPTC Series B-2 Bonds (1)
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 | APTC 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 | GPTC Securities
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Available-for-sale securities	0.0	0.0
Money Market Funds | Fair Value, Measurements, Recurring
Assets/Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents	4.0	44.1
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	4.0	44.1
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	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	$ 0.0