Business Segments - Revenue Information by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 10,595	$ 9,509
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	5,202	4,860
Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	2,477	2,434
Rest of Americas
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	618	652
Asia/Pacific Rim
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 2,298	$ 1,563