Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Oct. 02, 2020	Sep. 27, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity investments	$ 34.4	$ 0.0
Available-for- sale securities	44.9	$ 58.8
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity investments	54.6
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value	247.5
Derivative liabilities	(0.1)
Contingent consideration	(43.1)
Total liabilities measured at fair value	(43.2)
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value	148.0
Derivative liabilities	0.0
Contingent consideration	0.0
Total liabilities measured at fair value	0.0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value	99.5
Derivative liabilities	(0.1)
Contingent consideration	0.0
Total liabilities measured at fair value	(0.1)
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value	0.0
Derivative liabilities	0.0
Contingent consideration	(43.1)
Total liabilities measured at fair value	(43.1)
Fair Value, Measurements, Recurring | MPTC Series B-1 Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	18.9
Fair Value, Measurements, Recurring | MPTC Series B-1 Bonds | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	0.0
Fair Value, Measurements, Recurring | MPTC Series B-1 Bonds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	18.9
Fair Value, Measurements, Recurring | MPTC Series B-1 Bonds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	0.0
Fair Value, Measurements, Recurring | MPTC Series B-2 Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	20.6
Fair Value, Measurements, Recurring | MPTC Series B-2 Bonds | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	0.0
Fair Value, Measurements, Recurring | MPTC Series B-2 Bonds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	20.6
Fair Value, Measurements, Recurring | MPTC Series B-2 Bonds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	0.0
Fair Value, Measurements, Recurring | APTC securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	5.4
Fair Value, Measurements, Recurring | APTC securities | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	0.0
Fair Value, Measurements, Recurring | APTC securities | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	5.4
Fair Value, Measurements, Recurring | APTC securities | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Available-for- sale securities	0.0
Money Market Funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Money market funds	148.0
Equity investments	54.6
Money Market Funds | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Money market funds	148.0
Equity investments	0.0
Money Market Funds | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Money market funds	0.0
Equity investments	54.6
Money Market Funds | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Money market funds	0.0
Equity investments	$ 0.0