Business Segments - Revenue Information by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 10,002	$ 11,908	$ 20,485	$ 23,839
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	5,882	6,923	11,586	12,771
Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	1,840	2,297	3,775	4,588
Rest of Americas
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	555	762	1,164	1,382
Asia/Pacific Rim
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 1,725	$ 1,926	$ 3,960	$ 5,098