Business Segments and Geographic Information - Revenues by Geography (Detail)	12 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
Schedule Of Geographical Segments [Line Items]
Revenues	100.00%	100.00%	100.00%
United States
Schedule Of Geographical Segments [Line Items]
Revenues	75.30%	75.10%	77.60%
Europe
Schedule Of Geographical Segments [Line Items]
Revenues	11.80%	11.70%	10.00%
Asia-Pacific
Schedule Of Geographical Segments [Line Items]
Revenues	8.50%	8.60%	8.10%
Rest of world
Schedule Of Geographical Segments [Line Items]
Revenues	4.40%	4.60%	4.30%