CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017
Income Statement [Abstract]
Product	$ 55,374	$ 50,404
Service	34,753	32,539
Total net revenue	90,127	82,943
Product	26,609	26,102
Service	16,335	16,433
Total cost of revenue	42,944	42,535
Total gross profit	47,183	40,408
Operating expenses:
Research and development	23,457	24,882
Selling, general and administrative	31,163	34,631
Amortization of intangibles	804	774
Restructuring and related charges	1,086	1,279
Total operating expenses	56,510	61,566
Loss from operations	(9,327)	(21,158)
Interest expense, net	(2,757)	(2,590)
Other expense, net	(532)	(511)
Loss before income taxes	(12,616)	(24,259)
Provision for (benefit from) income taxes	1,078	(232)
Net loss	$ (13,694)	$ (24,027)
Net loss per share:
Basic and diluted	$ (0.16)	$ (0.30)
Shares used in per share calculation:
Basic and diluted	83,912	79,810