CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]
Common Stock, Beginning at Dec. 31, 2017			82,554
Balance at Dec. 31, 2017		$ 218,343	$ 83	$ 2,272,690	$ (2,057,812)	$ 3,382
Cumulative effect to retained earnings related to adoption of Topic 718 | Accounting Standards Update 2014-09 [Member]		11,431			11,431
Common Stock, Ending at Jan. 01, 2018			82,554
Balance at Jan. 01, 2018		229,774	$ 83	2,272,690	(2,046,381)	3,382
Common Stock, Beginning at Dec. 31, 2017			82,554
Balance at Dec. 31, 2017		218,343	$ 83	2,272,690	(2,057,812)	3,382
Net loss		(16,607)			(16,607)
Other comprehensive loss, net of tax		(3,393)				(3,393)
Issuance of common stock under option, stock award and purchase plans, Shares			2,885
Issuance of common stock under option, stock award and purchase plans, Value		2,312	$ 2	2,310
Additional Paid-in Capital, Stock-based compensation		8,649		8,649
Common Stock, Ending at Jun. 29, 2018			85,439
Balance at Jun. 29, 2018		220,735	$ 85	2,283,649	(2,062,988)	(11)
Common Stock, Beginning at Dec. 31, 2018			87,057
Balance at Dec. 31, 2018		228,250	$ 87	2,296,795	(2,067,416)	(1,216)
Cumulative effect to retained earnings related to adoption of Topic 718 | Accounting Standards Update 2016-09 [Member]	[1]	1,400			1,400
Common Stock, Ending at Jan. 01, 2019			87,057
Balance at Jan. 01, 2019		229,650	$ 87	2,296,795	(2,066,016)	(1,216)
Common Stock, Beginning at Dec. 31, 2018			87,057
Balance at Dec. 31, 2018		228,250	$ 87	2,296,795	(2,067,416)	(1,216)
Net loss		(23,151)
Other comprehensive loss, net of tax		(438)				(438)
Issuance of common stock under option, stock award and purchase plans, Shares			2,017
Issuance of common stock under option, stock award and purchase plans, Value		1,319	$ 2	1,317
Additional Paid-in Capital, Stock-based compensation		4,686		4,686
Common Stock, Ending at Jun. 28, 2019			89,074
Balance at Jun. 28, 2019		$ 212,066	$ 89	$ 2,302,798	$ (2,089,167)	$ (1,654)

[1] See Note 2, “Recent Accounting Pronouncements” for more information on the adoption of Accounting Standard Update (“ASU”) No. 2018-07, Compensation-Stock Compensation (“Topic 718”): Improvements to Nonemployee Share-Based Payment Accounting issued by the Financial Accounting Standards Board.