Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017
Summary of Finite-lived intangible assets
Adjusted cost	$ 34,584	$ 32,584
Accumulated amortization	(30,448)	(30,378)
Finite lived intangible assets, Net carrying amount	4,136	2,206
Developed technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	20,887	18,887
Accumulated amortization	(16,751)	(16,681)
Finite lived intangible assets, Net carrying amount	4,136	2,206
Customer relationships [Member]
Summary of Finite-lived intangible assets
Adjusted cost	9,438	9,438
Accumulated amortization	(9,438)	(9,438)
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)	(1,927)
Finite lived intangible assets, Net carrying amount	0	0
Patented technology [Member]
Summary of Finite-lived intangible assets
Adjusted cost	2,252	2,252
Accumulated amortization	(2,252)	(2,252)
Finite lived intangible assets, Net carrying amount	0	0
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