Note 10 - Income Taxes (Details Textual) - USD ($) $ in Thousands		12 Months Ended
	Dec. 22, 2017	Jan. 03, 2021	Dec. 29, 2019	Dec. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%	21.00%
Unrecognized Tax Benefits, Ending Balance		$ 2,176	$ 2,117	$ 2,161		$ 2,107
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		0
Federal [Member]
Operating Loss Carryforwards, Total		181,100			$ 39,200	$ 141,600
Federal [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount		4,100
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total		81,000
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount		$ 4,600