Employee Stock Plans - Summary of Share-Based Awards Available for Grant (Detail) - shares shares in Millions		12 Months Ended
	Feb. 08, 2018	Sep. 28, 2018	Sep. 29, 2017	Sep. 30, 2016
Shares Available for Grant
Beginning balance (in shares)		2.5	4.6	6.7
Authorized (in shares)		6.0
Granted (in shares)		(1.9)	(1.8)	(2.4)
Canceled or expired (in shares)		0.5	0.3	0.3
Adjustment due to Distribution (in shares)			(0.6)
Ending balance (in shares)		7.1	2.5	4.6
Fifth Amended 2005 Plan
Shares Available for Grant
Authorized (in shares)	6.0