Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 26, 2015
Summary of Finite-lived intangible assets
Adjusted cost	$ 29,982	$ 29,721
Accumulated amortization	(29,430)	(27,854)
Finite lived intangible assets, Net carrying amount	552	1,867
Developed technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	16,336	16,098
Accumulated amortization	(15,867)	(14,387)
Finite lived intangible assets, Net carrying amount	469	1,711
Customer relationships [Member]
Summary of Finite-lived intangible assets
Adjusted cost	9,387	9,364
Accumulated amortization	(9,387)	(9,364)
Finite lived intangible assets, Net carrying amount	0	0
Brand names [Member]
Summary of Finite-lived intangible assets
Adjusted cost	1,927	1,927
Accumulated amortization	(1,927)	(1,903)
Finite lived intangible assets, Net carrying amount	0	24
Patented technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	2,252	2,252
Accumulated amortization	(2,169)	(2,120)
Finite lived intangible assets, Net carrying amount	83	132
Trademark [Member]
Summary of Finite-lived intangible assets
Adjusted cost	80	80
Accumulated amortization	(80)	(80)
Finite lived intangible assets, Net carrying amount	$ 0	$ 0