Employee Stock Plans - Summary of Share-Based Awards Available for Grant (Detail) - shares shares in Millions	12 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Oct. 02, 2015
Shares Available for Grant
Beginning balance (in shares)	4.6	6.7	8.2
Granted (in shares)	(1.8)	(2.4)	(1.8)
Canceled or expired (in shares)	0.3	0.3	0.3
Adjustment due to Distribution (in shares)	(0.6)
Ending balance (in shares)	2.5	4.6	6.7