Business Segments and Geographic Information - Revenues by Geography (Detail)	3 Months Ended
	Dec. 26, 2020	Dec. 28, 2019
Schedule Of Geographical Segments [Line Items]
Revenues	100.00%	100.00%
United States
Schedule Of Geographical Segments [Line Items]
Revenues	70.70%	74.40%
Europe
Schedule Of Geographical Segments [Line Items]
Revenues	21.00%	12.90%
Asia-Pacific
Schedule Of Geographical Segments [Line Items]
Revenues	5.50%	8.30%
Rest of World
Schedule Of Geographical Segments [Line Items]
Revenues	2.80%	4.40%