Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 04, 2020	Jun. 29, 2019	Jul. 04, 2020	Jun. 29, 2019
Income Statement [Abstract]
Net sales	$ 298,330	$ 339,170	$ 912,248	$ 1,095,176
Cost of sales	203,053	241,167	613,607	717,106
Gross profit	95,277	98,003	298,641	378,070
Operating expenses:
Research and development	28,283	30,692	86,757	90,095
Selling, general and administrative	67,525	67,686	197,383	201,706
Goodwill and other impairment charges	0	0	451,025	0
Amortization of intangible assets	643	6,782	3,371	11,748
Total operating expenses	96,451	105,160	738,536	303,549
Income (loss) from operations	(1,174)	(7,157)	(439,895)	74,521
Other income (expense):
Interest income	269	257	906	903
Interest expense	(4,046)	(4,974)	(12,563)	(14,794)
Other—net	(505)	331	(1,322)	(3,898)
Total other expense, net	(4,282)	(4,386)	(12,979)	(17,789)
Income (loss) before income taxes	(5,456)	(11,543)	(452,874)	56,732
Provision for (benefit from) income taxes	3,252	(8,444)	(31,046)	3,531
Net income (loss)	$ (8,708)	$ (3,099)	$ (421,828)	$ 53,201
Net income (loss) per share:
Basic (in USD per share)	$ (0.36)	$ (0.13)	$ (17.52)	$ 2.20
Diluted (in USD per share)	$ (0.36)	$ (0.13)	$ (17.52)	$ 2.19
Shares used in computation:
Basic (shares)	24,159	24,054	24,075	24,185
Diluted (shares)	24,159	24,054	24,075	24,333