Note 10 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Jan. 01, 2022	Mar. 25, 2021	Sep. 17, 2020	May 22, 2020	Dec. 31, 2021	Dec. 31, 2020	Mar. 24, 2022	Jan. 31, 2021	May 06, 2020	Dec. 06, 2019
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)
Proceeds from Issuance of Common Stock					$ 4,843	$ 0
Fair Value Adjustment of Warrants					$ 0	$ 1,112
The 2011 Long-term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)								1,535,500
The 2020 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)					631,000	230,000
Subsequent Event [Member] | The 2020 Equity Incentive Plan [Member]
Share-based Compensation Plan, Annual Increases to Shares of Common Stock Issued and Outstanding	4.00%
March 2021 Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 3.60
Warrants and Rights Outstanding, Term (Year)		5 years
Over Allotment Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				413,793
Series I Warrants Issued with Offering [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)									$ 9.67	$ 12.09
Series I and F Warrants Issued with Offering [Member]
Fair Value Adjustment of Warrants					$ 1,100
March 2021 Public Offering [Member]
Equity Issued During Period, Units, New Issues (in shares)		9,230,500
Units, Number of Securities Called by Each Unit (in shares)		1
Stock and Warrants Issued, Price Per Share (in dollars per share)		$ 3.25
Proceeds from Issuance or Sale of Equity, Gross Amount		$ 30,000
Proceeds from Issuance or Sale of Equity, Total		$ 27,400
Public Offering [Member]
Equity Issued During Period, Units, New Issues (in shares)				2,758,620
Units, Number of Securities Called by Each Unit (in shares)				1
Proceeds from Issuance or Sale of Equity, Total				$ 20,200
Units Issued, Price Per Unit (in dollars per share)				$ 7.25
Payments of Stock Issuance Costs				$ 2,800
Public Offering [Member] | Warrants Issued in Units [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 7.975
Warrants and Rights Outstanding, Term (Year)				5 years
Over-Allotment Option [Member]
Equity Issued During Period, Units, New Issues (in shares)				413,793
ATM Program [Member]
Shares Authorized to Be Offered and Sold Under Offering Agreement, Value			$ 10,000
Stock Issued During Period, Shares, New Issues (in shares)					2,116,944
Stock Issued During Period, Value, New Issues					$ 5,000
Proceeds from Issuance of Common Stock					$ 4,800
ATM Program [Member] | Subsequent Event [Member]
Stock Offering Agreement, Remaining Amount Available							$ 5,000
ATM Program [Member] | Ladenburg [Member]
Commission Fee, Percent Fee			3.00%