Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2016	Jun. 27, 2015	Jun. 25, 2016	Jun. 27, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 6,031	$ 1,344	$ 9,498	$ 3,900
Other comprehensive income (loss):
Change in foreign currency translation adjustment	547	(18)	1,499	(1,745)
Net change on unrealized gains on available-for-sale investments	37	(4)	72	25
Other comprehensive income (loss):	584	(22)	1,571	(1,720)
Comprehensive income	$ 6,615	$ 1,322	$ 11,069	$ 2,180