Schedule II-Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period		$ 37,249
End of period		58,411	$ 37,249
Allowance for doubtful accounts [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period		385	79	$ 506
Charged to Costs and Expenses		212	383	(136)
Other Additions		0	0	0
Other Deductions	[1]	0	(77)	(291)
End of period		597	385	79
Inventory reserve [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period		26,889	24,639	21,080
Charged to Costs and Expenses		2,657	4,897	10,925
Other Additions		0	0	0
Other Deductions	[2]	(233)	(2,647)	(7,366)
End of period		29,313	26,889	24,639
Valuation allowance for deferred taxes [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning of period		37,249	29,614	27,381
Charged to Costs and Expenses	[3]	0	0	0
Other Additions		21,162	7,635	2,233
Other Deductions		0	0	0
End of period		$ 58,411	$ 37,249	$ 29,614

[1] Represents write-offs of specific accounts receivable.

[2] Sale or scrap of previously reserved inventory.

[3] Reflects increase/decrease in the valuation allowance primarily associated with the Company's U.S. and foreign net operating losses and other deferred tax assets.