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]	Convertible Note due 2020
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]	1,400			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	(11,306)			(11,306)
Other comprehensive loss, net of tax	(1,249)				(1,249)
Issuance of common stock under option, stock award and purchase plans, Shares		1,727
Issuance of common stock under option, stock award and purchase plans, Value	1,355	$ 2	1,353
Stock-based compensation	2,111		2,111
Common Stock, Ending at Mar. 29, 2019		88,784
Balance at Mar. 29, 2019	220,561	$ 89	2,300,259	(2,077,322)	(2,465)
Common Stock, Beginning at Dec. 31, 2019		91,875
Balance at Dec. 31, 2019	252,446	$ 92	2,327,359	(2,071,940)	(3,065)
Net loss	(21,954)			(21,954)
Other comprehensive loss, net of tax	(3,275)				(3,275)
Issuance of common stock under option, stock award and purchase plans, Shares		2,278
Issuance of common stock under option, stock award and purchase plans, Value	2,171	$ 3	2,168
Stock-based compensation	6,301		6,301
Issuance of warrant, shares		2,413
Issuance of warrant, amount		$ 2
Issuance of warrant, Additional Paid-in Capital	0		(2)
Reclassification from mezzanine equity to equity for 4.00% Convertible Senior Notes due in 2020	633		633
Common Stock, Ending at Mar. 27, 2020		96,566
Balance at Mar. 27, 2020	$ 236,322	$ 97	$ 2,336,459	$ (2,093,894)	$ (6,340)
Debt Instrument, Interest Rate, Stated Percentage						4.00%