Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Accumulated Other Comprehensive Income	Additional Paid-in Capital	Accumulated Deficit
Treasury Stock, Shares			(23)
Balance at beginning of period, (in shares) at Sep. 28, 2018		65,202
Balance at beginning of period at Sep. 28, 2018	$ 668,675	$ 65	$ (330)	$ 2,188	$ 1,074,728	$ (407,976)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		23
Stock options exercises	46				46
Vesting of restricted common stock and units (in shares)		632
Vesting of restricted common stock and units	1	$ 1
Issuance of common stock pursuant to employee stock purchase plan (in shares)		421
Issuance of common stock pursuant to employee stock purchase plan	5,585				5,585
Shares repurchased for stock withholdings on restricted stock awards (in shares)		(223)
Shares repurchased for tax withholdings on equity awards	(3,872)				(3,872)
Share-based compensation	20,163				20,163
Other comprehensive loss, net of tax	2,711			2,711
Net loss	(394,314)					(394,314)
Balance at end of period, (in shares) at Jun. 28, 2019		66,055
Balance at end of period at Jun. 28, 2019	298,995	$ 66	$ (330)	4,899	1,096,650	(802,290)
Treasury Stock, Shares			(23)
Balance at beginning of period, (in shares) at Mar. 29, 2019		65,723
Balance at beginning of period at Mar. 29, 2019	617,025	$ 66	$ (330)	3,798	1,091,067	(477,576)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		11
Stock options exercises	22				22
Vesting of restricted common stock and units (in shares)		87
Vesting of restricted common stock and units	0	$ 0
Issuance of common stock pursuant to employee stock purchase plan (in shares)		265
Issuance of common stock pursuant to employee stock purchase plan	3,193				3,193
Shares repurchased for stock withholdings on restricted stock awards (in shares)		(31)
Shares repurchased for tax withholdings on equity awards	(446)				(446)
Share-based compensation	2,814				2,814
Other comprehensive loss, net of tax	1,101			1,101
Net loss	(324,714)					(324,714)
Balance at end of period, (in shares) at Jun. 28, 2019		66,055
Balance at end of period at Jun. 28, 2019	298,995	$ 66	$ (330)	4,899	1,096,650	(802,290)
Treasury Stock, Shares			(23)
Treasury Stock, Shares			(23)
Balance at beginning of period, (in shares) at Sep. 27, 2019		66,177
Balance at beginning of period at Sep. 27, 2019	$ 313,896	$ 66	$ (330)	4,358	1,101,576	(791,774)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)	41	41
Stock options exercises	$ 168				168
Vesting of restricted common stock and units (in shares)		636
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 stock withholdings on restricted stock awards (in shares)		(223)
Shares repurchased for tax withholdings on equity awards	(6,557)				(6,557)
Share-based compensation	26,921				26,921
Other comprehensive loss, net of tax	(77)			(77)
Net loss	(63,570)					(63,570)
Balance at end of period, (in shares) at Jul. 03, 2020		66,903
Balance at end of period at Jul. 03, 2020	273,304	$ 67	$ (330)	4,281	1,126,505	(857,219)
Treasury Stock, Shares			(23)
Balance at beginning of period, (in shares) at Apr. 03, 2020		66,718
Balance at beginning of period at Apr. 03, 2020	285,731	$ 67	$ (330)	2,126	1,116,105	(832,237)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		23
Stock options exercises	46				46
Vesting of restricted common stock and units (in shares)		72
Vesting of restricted common stock and units	0	$ 0
Issuance of common stock pursuant to employee stock purchase plan (in shares)		112
Issuance of common stock pursuant to employee stock purchase plan	2,467				2,467
Shares repurchased for stock withholdings on restricted stock awards (in shares)		(22)
Shares repurchased for tax withholdings on equity awards	(608)				(608)
Share-based compensation	8,495				8,495
Other comprehensive loss, net of tax	2,155			2,155
Net loss	(24,982)					(24,982)
Balance at end of period, (in shares) at Jul. 03, 2020		66,903
Balance at end of period at Jul. 03, 2020	273,304	$ 67	$ (330)	$ 4,281	$ 1,126,505	(857,219)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ (1,875)					$ (1,875)
Treasury Stock, Shares			(23)