Summary of Significant Accounting Policies - Schedule of Other Assets (Detail) - USD ($)	Sep. 26, 2020	Sep. 29, 2019	Sep. 28, 2019
Accounting Policies [Abstract]
Income Taxes Receivable	$ 325,700,000		$ 0
Operating lease, right-of-use assets	80,700,000	$ 91,700,000	0
Life insurance contracts	49,300,000		44,600,000
Manufacturing access fees	15,500,000		17,200,000
Cost-method equity investments	11,400,000		11,400,000
Equity-method investment and loans to SSI (Note 5)	0		42,700,000
Other	34,000,000.0		38,700,000
Other assets	$ 516,600,000		$ 154,600,000