Geographic and Group Information (Geographic Revenue before Reimbursements) (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2022	Apr. 02, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 75,664	$ 63,486
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	64,392	55,259
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	7,537	5,558
Other (Australia, Canada, India and Uruguay) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 3,735	$ 2,669