CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (43,052)	$ (12,414)	$ (63,349)	$ (45,935)
Other comprehensive loss:
Unrealized loss related to marketable securities, net of tax	(1)	(61)	(72)	(88)
Reclassification adjustment for losses related to marketable securities included in other income, net of tax	37	0	237	38
Translation adjustment, net of tax	431	(138)	1,381	(579)
Change in actuarial valuation of defined benefit pension	0	0	(47)	141
Comprehensive loss	$ (42,585)	$ (12,613)	$ (61,850)	$ (46,423)