Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jun. 25, 2016	Jul. 01, 2017	Jun. 25, 2016
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 18,475	$ 15,265	$ 30,311	$ 35,393
Other comprehensive income (loss) by component, net of tax:
Available-for-sale marketable securities Unrealized holding gains arising during period (Net of deferred taxes of $137 and $353, respectively for the 13 Weeks Ended and $126 and $922, respectively for the 26 Weeks Ended)	(198)	506	(134)	1,322
Reclassification adjustment for gains included in net income (Net of deferred taxes of $0 and $111, respectively for the 26 Weeks Ended)				(158)
Other comprehensive income, net of tax	(198)	506	(134)	1,164
Comprehensive income, net of tax	$ 18,277	$ 15,771	$ 30,177	$ 36,557