CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (13,022)	$ (13,810)	$ (20,297)	$ (33,521)
Other comprehensive loss:
Unrealized (loss) gain related to marketable securities, net of tax	(28)	1	(71)	(27)
Reclassification adjustment for losses related to marketable securities included in other income, net of tax	30	36	200	38
Translation adjustment, net of tax	676	(678)	950	(441)
Change in actuarial valuation of defined benefit pension	(47)	141	(47)	141
Comprehensive loss	$ (12,391)	$ (14,310)	$ (19,265)	$ (33,810)

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities, attributable to parent entity. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan, attributable to parent.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to parent entity.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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