Business Segments - Revenue Information by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 10,865	$ 9,789	$ 31,350	$ 33,628
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	6,294	5,871	17,880	18,642
Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	1,727	2,191	5,502	6,779
Rest of Americas
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	689	476	1,853	1,858
Asia/Pacific Rim
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 2,155	$ 1,251	$ 6,115	$ 6,349