CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 28, 2019	Sep. 30, 2020	Sep. 28, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (5,088)	$ (8,280)	$ (22,437)	$ (24,370)
Other comprehensive income (loss):
Foreign currency translation adjustment	16	56	(10)	69
Unrealized gains (losses) on marketable securities, net of tax of $0	(68)	22	(4)	52
Total other comprehensive income (loss)	(52)	78	(14)	121
Comprehensive loss	$ (5,140)	$ (8,202)	$ (22,451)	$ (24,249)