Geographic and Service Group Information (Geographic Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 30, 2016	Jul. 01, 2016	Apr. 01, 2016	Dec. 29, 2017	Dec. 30, 2016	Jan. 01, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 64,510	$ 65,947	$ 67,726	$ 65,069	$ 62,946	$ 66,810	$ 68,178	$ 61,973	$ 285,862	$ 288,561	$ 260,940
North America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									230,904	246,249	218,719
International (Primarily European Countries) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 54,958	$ 42,312	$ 42,221