Income Taxes - Reconciliation of the Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Oct. 01, 2017	Oct. 02, 2016	Sep. 27, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning gross unrecognized tax benefits	$ 319.0	$ 121.8	$ 97.7
Additions based on tax positions related to the current year	21.8	33.1	3.5
Additions based on current year acquisitions	0.4	132.6	16.2
Additions based on tax positions of prior years	3.4	36.3	4.8
Reductions based on tax positions of prior years	65.9	0.0	0.0
Reductions for lapses and settlements	(0.2)	(4.8)	(0.4)
Ending gross unrecognized tax benefit	$ 278.5	$ 319.0	$ 121.8