Note 15 - Quarterly Financial Data (Unaudited) - Schedule of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 02, 2021	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Revenue	$ 107,173	$ 103,042	$ 100,589	$ 97,316	$ 100,237	$ 103,469	$ 102,296	$ 98,091	$ 408,120	$ 404,093	$ 398,799
Gross margin	64,861	62,306	60,577	57,562	59,293	61,439	60,038	57,652	245,306	238,422	219,439
Restructuring and Related Costs, Incurred Cost, Total	(241)	2,692	546	940	(55)	252	3,126	1,341
Net income	$ 15,989	$ 12,607	$ 10,629	$ 8,167	$ 13,987	$ 13,539	$ 8,559	$ 7,408	$ 47,392	$ 43,493	$ (26,322)
Net income per share - basic (in dollars per share)	$ 0.12	$ 0.09	$ 0.08	$ 0.06	$ 0.10	$ 0.10	$ 0.06	$ 0.06	$ 0.35	$ 0.33	$ (0.21)
Net income per share - diluted (in dollars per share)	$ 0.11	$ 0.09	$ 0.08	$ 0.06	$ 0.10	$ 0.10	$ 0.06	$ 0.05	$ 0.34	$ 0.32	$ (0.21)