Business Segments - Revenue Information by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 10,426	$ 10,304	$ 21,021	$ 19,813
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	5,327	5,114	10,529	9,974
Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	2,587	2,226	5,064	4,660
Rest of Americas
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	754	656	1,372	1,308
Asia/Pacific Rim
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 1,758	$ 2,308	$ 4,056	$ 3,871