Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Additional Paid-In Capital	Accumulated Deficit
Beginning Balance (in shares) at Sep. 29, 2017		64,279
Beginning balance at Sep. 29, 2017	$ 777,374	$ 64	$ (330)	$ 2,977	$ 1,041,644	$ (266,981)
Beginning Balance Treasury stock (in shares) at Sep. 29, 2017			(23)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercise (in shares)		27
Stock option exercises	76				76
Vesting of restricted common stock and units (in shares)		906
Vesting of restricted common stock and units	1	$ 1
Issuance of common stock pursuant to employee stock purchase plan (in shares)		306
Issuance of common stock pursuant to employee stock purchase plan	6,881				6,881
Shares repurchased for tax withholdings on restricted stock awards (in shares)		(316)
Shares repurchased for tax withholdings on restricted stock awards	(6,828)	$ 0			(6,828)
Share-based compensation	31,937				31,937
Other comprehensive loss, net of tax	(789)			(789)
Net loss	(139,977)					(139,977)
Ending Balance (in shares) at Sep. 28, 2018		65,202
Ending balance at Sep. 28, 2018	668,675	$ 65	$ (330)	2,188	1,074,728	(407,976)
Ending Balance Treasury stock (in shares) at Sep. 28, 2018			(23)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption					1,018	(1,018)
Stock option exercise (in shares)		119
Stock option exercises	1,608				1,608
Vesting of restricted common stock and units (in shares)		673
Vesting of restricted common stock and units	1	$ 1
Issuance of common stock pursuant to employee stock purchase plan (in shares)		422
Issuance of common stock pursuant to employee stock purchase plan	5,585				5,585
Shares repurchased for tax withholdings on restricted stock awards (in shares)		(239)
Shares repurchased for tax withholdings on restricted stock awards	(4,137)				(4,137)
Share-based compensation	23,792				23,792
Other comprehensive loss, net of tax	2,170			2,170
Net loss	(383,798)					(383,798)
Ending Balance (in shares) at Sep. 27, 2019		66,177
Ending balance at Sep. 27, 2019	$ 313,896	$ 66	$ (330)	4,358	1,101,576	(791,774)
Ending Balance Treasury stock (in shares) at Sep. 27, 2019	23		(23)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 0
Stock option exercise (in shares)	51	51
Stock option exercises	$ 188	$ 0			188
Vesting of restricted common stock and units (in shares)		648
Vesting of restricted common stock and units	1	$ 1
Issuance of common stock pursuant to employee stock purchase plan (in shares)		272
Issuance of common stock pursuant to employee stock purchase plan	4,397				4,397
Shares repurchased for tax withholdings on restricted stock awards (in shares)		(227)
Shares repurchased for tax withholdings on restricted stock awards	(6,708)	$ 0			(6,708)
Share-based compensation	35,674				35,674
Other comprehensive loss, net of tax	651			651
Net loss	(46,078)					(46,078)
Ending Balance (in shares) at Oct. 02, 2020		66,921
Ending balance at Oct. 02, 2020	$ 300,146	$ 67	$ (330)	$ 5,009	1,135,127	(839,727)
Ending Balance Treasury stock (in shares) at Oct. 02, 2020	23		(23)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (1,875)				$ 0	$ (1,875)