Business Segments - Revenue Information by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 9,021	$ 10,595
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	4,441	5,202
Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	1,984	2,477
Rest of Americas
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	403	618
Asia/Pacific Rim
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenues	$ 2,193	$ 2,298