Operating Segments and Geographic Data (Revenue By Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 30, 2016	Jul. 01, 2016	Apr. 01, 2016	Jan. 01, 2016	Sep. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenue	$ 242,048	$ 305,665	$ 267,474	$ 266,267	$ 232,997	$ 277,587	$ 274,340	$ 240,814	$ 1,081,454	$ 1,025,738	$ 970,638
U.S. [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenue									373,264	320,129	276,733
International [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenue									$ 708,190	$ 705,609	$ 693,905