Significant Accounting Policies - Accounts receivable Allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Oct. 01, 2016
Accounts Receivable, Allowance for Doubtful Accounts [Roll Forward]
Beginning balance	$ 6,890	$ 2,420	$ 3,015
Additions charged to expenses	1,980	4,190	2,084
Accruals related to acquisitions	37	4,390	0
Deductions from reserves	(4,339)	(4,110)	(2,679)
Ending balance	$ 4,568	$ 6,890	$ 2,420