Note 10 - Business Unit Segment Information - Net Sales by Geographic Area (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
UNITED STATES
Net sales	[1]	$ 85,049	$ 85,326	$ 258,030	$ 243,979
CHINA
Net sales	[1]	49,345	45,905	143,694	134,166
Other Countries [Member]
Net sales	[1]	81,116	86,377	246,120	267,230
Net sales	[1]	$ 215,510	$ 217,608	$ 647,844	$ 645,375

[1] Sales by country represent sale to customer or distributor locations.