Note 9 - Income Taxes (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 25, 2021	Dec. 26, 2020	Dec. 28, 2019
Deferred Tax Assets, Valuation Allowance, Total	$ 76,250	$ 86,124
Increase (Decrease) of Net Income Due to Impact of Tax Holidays	$ 4,500	$ 3,600	$ 2,100
Increase (Decrease) of Earning Per Share Due To Impact Of Tax Holidays (in dollars per share)	$ 0.09	$ 0.09	$ 0.05
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 5,300	$ 5,900	$ 7,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	800	1,000
Unrecognized Tax Benefits, Interest Expense, Net of Accrued Interest Reversed	$ (200)	$ (300)	$ (300)
Minimum [Member]
Collection Term Range (Year)	4 years
Maximum [Member]
Collection Term Range (Year)	10 years
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	$ 160,500
Tax Credit Carryforward, Amount	$ 6,800
Open Tax Year	2016 2017 2018 2019 2020 2021
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 135,300
Tax Credit Carryforward, Amount	30,900
Foreign Tax Authority [Member]
Operating Loss Carryforwards, Total	$ 9,600