Geographic and Group Information (Long-Lived Assets Attributable To Geographic Area) (Details) - USD ($) $ in Thousands	Sep. 27, 2019	Dec. 28, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 115,956	$ 107,661
North America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	92,745	88,317
International (Primarily European Countries) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 23,211	$ 19,344