Segment and Geographic Information - Revenue and Long-Lived Assets by Geographical Areas (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 03, 2020	Jul. 04, 2020	Apr. 04, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Oct. 03, 2020	Sep. 28, 2019	Sep. 29, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 316,751	$ 298,330	$ 293,147	$ 320,771	$ 335,464	$ 339,170	$ 372,860	$ 383,146	$ 1,228,999	$ 1,430,640	$ 1,902,573
Total long-lived assets	385,366				373,961				385,366	373,961
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									296,102	339,585	309,495
Total long-lived assets	170,412				151,640				170,412	151,640
Foreign Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									932,897	1,091,055	1,593,078
Total long-lived assets	214,954				222,321				214,954	222,321
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									247,461	313,461	652,313
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									196,824	194,653	235,568
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									94,068	138,028	180,223
Asia-Pacific, other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									94,835	93,389	124,733
Total long-lived assets	56,125				39,977				56,125	39,977
Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									117,170	145,285	166,926
Total long-lived assets	123,019				152,529				123,019	152,529
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									125,739	148,680	171,936
Total long-lived assets	$ 35,810				$ 29,815				35,810	29,815
Rest of World
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									$ 56,800	$ 57,559	$ 61,379