Geographic and Group Information (Geographic Revenue before Reimbursements) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2022	Jul. 02, 2021	Jul. 01, 2022	Jul. 02, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 75,928	$ 73,197	$ 151,592	$ 136,683
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	66,717	63,959	131,110	119,218
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	5,103	5,641	12,640	11,199
Other (Australia, Canada, India and Uruguay) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 4,108	$ 3,597	$ 7,842	$ 6,266