Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2017	Sep. 25, 2016	Oct. 01, 2017	Sep. 25, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 2,802	$ 21	$ 2,087	$ (1,927)
Other comprehensive loss, net of tax:
Unrealized gains (losses) on available-for-sale marketable securities	12	0	(20)	0
Comprehensive income (loss)	$ 2,814	$ 21	$ 2,067	$ (1,927)