Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 03, 2020	Mar. 29, 2019	Apr. 03, 2020	Mar. 29, 2019
Income Statement [Abstract]
Revenue	$ 126,424	$ 128,465	$ 245,521	$ 279,154
Cost of revenue	63,054	71,135	123,947	145,199
Gross profit	63,370	57,330	121,574	133,955
Operating expenses:
Research and development	35,830	42,361	70,988	85,885
Selling, general and administrative	31,994	41,998	64,334	84,518
Restructuring charges	815	3,182	2,049	8,160
Total operating expenses	68,639	87,541	137,371	178,563
Loss from operations	(5,269)	(30,211)	(15,797)	(44,608)
Other expense:
Warrant liability gain (expense)	8,647	(1,607)	4,560	3,862
Interest expense, net	(7,672)	(9,402)	(16,293)	(18,175)
Other expense, net	(4,352)	(4,440)	(8,092)	(9,010)
Total other expense net	(3,377)	(15,449)	(19,825)	(23,323)
Loss before income taxes	(8,646)	(45,660)	(35,622)	(67,931)
Income tax expense	1,580	544	2,966	1,669
Net loss	$ (10,226)	$ (46,204)	$ (38,588)	$ (69,600)
Basic loss per share:
Loss per share - basic	$ (0.15)	$ (0.71)	$ (0.58)	$ (1.06)
Diluted loss per share:
Loss per share - diluted	$ (0.28)	$ (0.71)	$ (0.64)	$ (1.12)
Shares used:
Basic (in shares)	66,522	65,531	66,375	65,404
Diluted (in shares)	67,085	65,531	66,921	65,610