Income Taxes - Activity of Company's Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 24, 2022	Sep. 25, 2021
Income Tax Disclosure [Abstract]
Balance at beginning of fiscal year	$ 212.8	$ 197.1
Tax positions related to current year:
Additions	45.9	8.0
Reductions	0.0	0.0
Tax positions related to prior years:
Additions related to change in estimate	21.5	7.9
Reductions	(6.6)	(0.3)
Payments	0.0	0.0
Lapses in statutes of limitations and settlements	(26.0)	(1.7)
Acquired tax positions:
Additions related to reserves acquired from acquisitions	0.0	1.8
Balance as of the end of the fiscal year	$ 247.6	$ 212.8