Restructurings- Additional Details (Details)	3 Months Ended	12 Months Ended
	Jul. 03, 2020 employee facility	Oct. 02, 2020 USD ($)	Sep. 27, 2019 USD ($)	Sep. 28, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring cost		$ 1,139,000	$ 19,543,000	$ 6,265,000
Employee related costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost		378,000	8,084,000	2,789,000
Facility related expenses
Restructuring Cost and Reserve [Line Items]
Restructuring cost		761,000	11,459,000	3,476,000
2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | employee	250
Number of facilities | facility	6
Restructuring cost		1,197,000	11,565,000
2019 Restructuring Plan | Employee related costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost		378,000	6,265,000
2019 Restructuring Plan | Facility related expenses
Restructuring Cost and Reserve [Line Items]
Restructuring cost		819,000	5,300,000
2019 Restructuring Plan | Fixed Asset Impairment
Restructuring Cost and Reserve [Line Items]
Restructuring cost			4,000,000.0
2019 Restructuring Plan | Other Costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost			1,300,000
Design Facility Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring cost		18,000	2,528,000
Design Facility Restructuring Plan | Employee related costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost		0	338,000
Design Facility Restructuring Plan | Facility related expenses
Restructuring Cost and Reserve [Line Items]
Restructuring cost		18,000	2,190,000
Ithaca Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring cost		40,000	5,450,000
Ithaca Restructuring Plan | Employee related costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost		0	1,481,000
Ithaca Restructuring Plan | Facility related expenses
Restructuring Cost and Reserve [Line Items]
Restructuring cost		40,000	3,969,000
Long Beach, Belfast and Sydney Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring cost		0	6,265,000	6,300,000
Long Beach, Belfast and Sydney Restructuring Plan | Employee related costs
Restructuring Cost and Reserve [Line Items]
Restructuring cost		0	2,789,000	2,800,000
Long Beach, Belfast and Sydney Restructuring Plan | Facility related expenses
Restructuring Cost and Reserve [Line Items]
Restructuring cost		$ 0	$ 3,476,000	$ 3,500,000