Business Segments and Geographic Information - Revenues by Geography (Detail)	3 Months Ended		9 Months Ended
	Jun. 25, 2016	Jun. 27, 2015	Jun. 25, 2016	Jun. 27, 2015
Schedule Of Geographical Segments [Line Items]
Revenues	100.00%	100.00%	100.00%	100.00%
United States
Schedule Of Geographical Segments [Line Items]
Revenues	78.70%	77.80%	78.70%	75.80%
Europe
Schedule Of Geographical Segments [Line Items]
Revenues	10.60%	11.30%	10.30%	12.20%
Asia-Pacific
Schedule Of Geographical Segments [Line Items]
Revenues	7.50%	7.90%	7.60%	8.50%
All others
Schedule Of Geographical Segments [Line Items]
Revenues	3.20%	3.00%	3.40%	3.50%