Segment Information (Geographic Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 02, 2020	Jun. 26, 2020	Mar. 27, 2020	Dec. 27, 2019	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 956,800	$ 736,800	$ 766,100	$ 896,100	$ 827,400	$ 767,000	$ 810,400	$ 972,000	$ 3,355,700	$ 3,376,800	$ 3,868,000
Contract with Customer, Refund Liability	$ 20,300				$ 38,500				20,300	38,500
Total Americas [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									2,012,800	1,860,400	1,946,200
China
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									700,700	718,700	982,800
Taiwan
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									240,400	271,100	339,100
South Korea
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									254,600	365,500	432,700
Asia
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									122,900	134,900	144,600
Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 24,300	$ 26,200	$ 22,600