CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2019		91,875
Beginning balance at Dec. 31, 2019	$ 252,446	$ 92	$ 2,327,359	$ (2,071,940)	$ (3,065)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(42,736)			(42,736)
Other comprehensive income (loss), net of tax	3,462				3,462
Issuance of common stock under stock option, award and purchase plans (in shares)		3,444
Issuance of common stock under stock option, award and purchase plans	3,843	$ 4	3,839
Stock-based compensation	13,768		13,768
Conversion feature of 2022 Notes	8,254		8,254
Reclassification from mezzanine equity to equity for 2020 Notes	2,329		2,329
Conversion feature of exchanged portion of 2020 Notes	(6,909)		(6,909)
Exercise of warrant (in shares)		2,413
Exercise of warrant	0	$ 2	(2)
Ending balance (in shares) at Sep. 25, 2020		97,732
Ending balance at Sep. 25, 2020	234,457	$ 98	2,348,638	(2,114,676)	397
Beginning balance (in shares) at Jun. 26, 2020		96,863
Beginning balance at Jun. 26, 2020	230,282	$ 97	2,342,856	(2,109,295)	(3,376)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(5,381)			(5,381)
Other comprehensive income (loss), net of tax	3,773				3,773
Issuance of common stock under stock option, award and purchase plans (in shares)		869
Issuance of common stock under stock option, award and purchase plans	1,892	$ 1	1,891
Stock-based compensation	3,972		3,972
Conversion feature of 2022 Notes	0
Reclassification from equity to mezzanine equity for Notes	(81)		(81)
Ending balance (in shares) at Sep. 25, 2020		97,732
Ending balance at Sep. 25, 2020	234,457	$ 98	2,348,638	(2,114,676)	397
Beginning balance (in shares) at Dec. 31, 2020		98,204
Beginning balance at Dec. 31, 2020	258,302	$ 98	2,353,559	(2,101,211)	5,856
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(6,603)			(6,603)
Other comprehensive income (loss), net of tax	(5,641)				(5,641)
Issuance of common stock under stock option, award and purchase plans (in shares)		4,345
Issuance of common stock under stock option, award and purchase plans	9,783	$ 5	9,778
Stock-based compensation	18,955		18,955
Reclassification from equity to mezzanine equity for Notes	(1,115)		(1,115)
Ending balance (in shares) at Oct. 01, 2021		102,549
Ending balance at Oct. 01, 2021	273,681	$ 103	2,381,177	(2,107,814)	215
Beginning balance (in shares) at Jul. 02, 2021		101,794
Beginning balance at Jul. 02, 2021	267,324	$ 102	2,373,851	(2,109,344)	2,715
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,530			1,530
Other comprehensive income (loss), net of tax	(2,500)				(2,500)
Issuance of common stock under stock option, award and purchase plans (in shares)		755
Issuance of common stock under stock option, award and purchase plans	1,908	$ 1	1,907
Stock-based compensation	6,534		6,534
Reclassification from equity to mezzanine equity for Notes	(1,115)		(1,115)
Ending balance (in shares) at Oct. 01, 2021		102,549
Ending balance at Oct. 01, 2021	$ 273,681	$ 103	$ 2,381,177	$ (2,107,814)	$ 215