Fair Value - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Oct. 02, 2020	Oct. 02, 2020	Sep. 28, 2018	Sep. 27, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Modified former loans receivable	$ 0.0	$ 0.0		$ 44.0
Equity investments in privately-held companies	68.2	68.2		64.2
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount		14.5
Equity investments	34.4	34.4		0.0
Unrealized gain on equity securities		25.5
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity investments	54.6	54.6
MPTC Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charges		16.9
APTC securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charges	0.9	0.9
Notes Receivable
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long term	36.7	$ 36.7		33.6
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Minimum remaining maturity of foreign currency derivatives (in months)		1 month
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Minimum remaining maturity of foreign currency derivatives (in months)		15 months
C P T C
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charges			$ 51.4
C P T C | Term Loan
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charges		$ 40.5
Modified former loans receivable	$ 11.8	$ 11.8		$ 49.3