Income Taxes (Reconciliation of Statutory Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2016	Dec. 29, 2015	Dec. 30, 2014
Income Tax Disclosure [Abstract]
Tax computed at U.S. federal statutory rate	$ 2,156	$ 330	$ (2,371)
State and local income taxes (net of federal benefit)	56	82	(179)
Tax credits	(4,590)	(5,219)	(5,772)
Charitable contributions	(324)	(560)	(475)
Change in deferred rate	(453)	(464)	1,130
Uncertain tax positions released	(156)	(71)	(755)
Other	568	134	(24)
Income tax benefit	$ (2,743)	$ (5,768)	$ (8,446)