CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 30, 2019	Sep. 26, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 8,091	$ 6,560	$ 11,111	$ 19,662
Other comprehensive income (loss), net of tax:
Change in net unrealized (losses) gains on available-for-sale marketable securities	(72)		197	209
Change in currency translation adjustments	1,803	(264)	2,067	(466)
Total other comprehensive income (loss), net of tax	1,731	(264)	2,264	(257)
Total comprehensive income	$ 9,822	$ 6,296	$ 13,375	$ 19,405