Restructuring (Details) $ in Thousands	12 Months Ended
	Sep. 28, 2018 USD ($) employee	Sep. 29, 2017 USD ($)	Sep. 30, 2016 USD ($) employee
Restructuring Reserve [Roll Forward]
Restructuring charges	$ 446	$ (12,856)	$ (1,233)
2016 Restructuring Plan [Member]
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance		0
Restructuring charges			(1,294)
Cash payments			(1,233)
Non-cash charges			(61)
Restructuring reserve, ending balance			$ 0
2013 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee			30
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		(12,856)
Cash payments		(168)
Non-cash charges		0
Restructuring reserve, ending balance		$ 12,688