Restructuring (Details) - USD ($)	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 256,000	$ 997,000
Charges	0	58,000
Cash Payments	(174,000)	(449,000)
Ending Balance	82,000	606,000
Employee severance and benefits [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0	383,000
Charges	0	45,000
Cash Payments	0	(308,000)
Ending Balance	0	120,000
Facility termination costs [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	249,000	583,000
Charges	0	0
Cash Payments	(174,000)	(106,000)
Ending Balance	75,000	477,000
Other [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	7,000	31,000
Charges	0	13,000
Cash Payments	0	(35,000)
Ending Balance	$ 7,000	$ 9,000