Note 6 - Stockholders' Equity and Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		3 Months Ended	12 Months Ended
	Jan. 01, 2023	Jun. 09, 2022	May 31, 2021	Nov. 30, 2017	Mar. 31, 2023	Dec. 31, 2017	Dec. 31, 2022	Feb. 04, 2021
Common Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001		$ 0.001
Time-based Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value					$ 49
Time-based Options [Member] | Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage					25.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)					1 year
Performance Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value					$ 1,800
The 2017 Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)						10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)						1,500,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)	1,200,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Number of Shares (in shares)						1,200,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Percent						4.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					3,136,838
The 2017 Inducement Equity Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)				10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)				1,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)			1,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					1,140,501
The 2017 Inducement Equity Incentive Plan [Member] | Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage				25.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)				1 year
The 2017 Employee Stock Purchase Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)						250,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Number of Shares (in shares)						450,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Percent						1.50%
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					198,529
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)					262,470
Maximum [Member] | The 2017 Inducement Equity Incentive Plan [Member] | Share-Based Payment Arrangement, Option [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)				10 years
Rights Offering Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)		1
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)					7,317,072
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 2.05			$ 2.05
Warrants and Rights Outstanding, Term (Year)					5 years
Class of Warrants or Rights, Redemption Price Per Share (in dollars per share)					$ 0.01
Class of Warrant or Right, Period of Written Notice for Exercise (Year)					30 years
Class of Warrant or Right, Percentage Required for Redemption					200.00%
Class of Warrant or Right, Exercise, Consecutive Trading Days (Year)					20 years
Class of Warrant or Right, Exercised During Period (in shares)					95,639
Class of Warrant or Right, Outstanding (in shares)					7,208,193
Rights Offering Warrants [Member] | Maximum [Member]
Additional Proceeds That May be Received Upon Exercise of Warrants		$ 15,000
Rights Offering [Member]
Equity Offering, Units, Sale of Units (in shares)		7,317,072
Shares Issued, Price Per Share (in dollars per share)		$ 2.05
Number of Shares Per Unit Issued (in shares)		1
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001
Number of Warrants Per Unit (in shares)		1
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)		1
Stock Issued During Period, Shares, New Issues (in shares)		7,317,072
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		7,317,072
Proceeds from Issuance of Common Stock		$ 15,000
Rights Offering [Member] | Board of Directors Chairman [Member]
Investment Owned, Percent of Net Assets		56.00%
ATM Offering [Member]
Equity Offering, Maximum Offering Amount								$ 60,000