Operating Segments and Geographic Data (Revenue By Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 28, 2018	Sep. 29, 2017	Sep. 30, 2016
Segment Reporting, Revenue Reconciling Item [Line Items]
Document Period End Date									Sep. 28, 2018
Total revenue	$ 265,325	$ 317,447	$ 301,355	$ 287,797	$ 242,048	$ 305,665	$ 267,474	$ 266,267	$ 1,171,924	$ 1,081,454	$ 1,025,738
U.S. [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenue									388,700	373,264	320,129
International [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenue									$ 783,224	$ 708,190	$ 705,609