Restructuring (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 28, 2018 USD ($)	Dec. 29, 2017 USD ($)	Sep. 29, 2017 USD ($) employee
Restructuring Reserve [Roll Forward]
Restructuring charges	$ (14)	$ 197
2017 Restructuring Plan [Member] [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee			80
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		$ 12,688
Restructuring charges	(23)		$ (12,856)
Cash payments	(12,054)		(168)
Non-cash charges	(537)		0
Restructuring reserve, ending balance	$ 120		$ 12,688