CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ 6,974	$ (43,052)	$ (19,201)	$ (63,349)
Other comprehensive income (loss:)
Unrealized gain (loss) related to marketable securities, net of tax	14	(1)	16	(72)
Reclassification adjustment for (gains) losses related to marketable securities included in other expense, net of tax	(17)	37	(18)	237
Translation adjustment, net of tax	(584)	431	(1,124)	1,381
Change in actuarial valuation of defined benefit pension	0	0	0	(47)
Comprehensive income (loss)	$ 6,387	$ (42,585)	$ (20,327)	$ (61,850)

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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