Business Segments and Geographic Information - Revenues by Geography (Detail)	3 Months Ended		9 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Schedule Of Geographical Segments [Line Items]
Revenues	100.00%	100.00%	100.00%	100.00%
United States
Schedule Of Geographical Segments [Line Items]
Revenues	80.30%	75.40%	76.90%	75.10%
Europe
Schedule Of Geographical Segments [Line Items]
Revenues	12.40%	11.30%	13.30%	12.00%
Asia-Pacific
Schedule Of Geographical Segments [Line Items]
Revenues	5.30%	8.90%	6.40%	8.40%
Rest of World
Schedule Of Geographical Segments [Line Items]
Revenues	2.00%	4.40%	3.40%	4.50%