Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 27, 2014
Summary of Finite-lived intangible assets
Adjusted cost	$ 29,946	$ 30,670
Accumulated amortization	(27,543)	(26,376)
Net carrying amount	2,403	4,294
Developed technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	16,299	16,950
Accumulated amortization	(14,094)	(12,991)
Net carrying amount	2,205	3,959
Customer relationships [Member]
Summary of Finite-lived intangible assets
Adjusted cost	9,388	9,461
Accumulated amortization	(9,388)	(9,449)
Net carrying amount	0	12
Brand names [Member]
Summary of Finite-lived intangible assets
Adjusted cost	1,927	1,927
Accumulated amortization	(1,877)	(1,802)
Net carrying amount	50	125
Patented technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	2,252	2,252
Accumulated amortization	(2,104)	(2,054)
Net carrying amount	148	198
Trademark [Member]
Summary of Finite-lived intangible assets
Adjusted cost	80	80
Accumulated amortization	(80)	(80)
Net carrying amount	$ 0	$ 0