Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 30,202	$ 44,035	$ 2,905
Other comprehensive income (loss):
Change in foreign currency translation adjustment	4,170	(869)	(2,344)
Employee benefit plan adjustment	(160)	(17)	(76)
Net change on unrealized (losses) gains on available-for-sale investments	(88)	42	(13)
Other comprehensive income (loss)	3,922	(844)	(2,433)
Comprehensive income	$ 34,124	$ 43,191	$ 472