Note 5 - Income Taxes - Reconciliation of Income Tax Computed at U.S. Federal Statutory Tax Rate to Provision (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Tax provision at U.S. 35% statutory rate	$ 12,378	$ 2,102	$ 2,801
Impact of Tax Act, before reduction in valuation allowance	12,397
State income taxes, net of federal tax benefit	56	168	(152)
Settlements, adjustments and releases from statute expirations	(1,731)	(312)	(104)
Federal tax credits	(371)	(183)	(221)
Stock-based compensation	(2,801)	168	156
Change in valuation allowance	(13,484)	2,430	2,181
Non-deductible transaction related costs	577	463
Foreign income taxed at different rates	(4,866)	(2,378)	(2,601)
Other, net	89	289	151
	$ 2,244	$ 2,747	$ 2,211