Note 9 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands				9 Months Ended
	Jun. 19, 2020	Jun. 18, 2020	Jun. 17, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Common Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001		$ 0.001
Proceeds from Issuance of Common Stock				$ 11,500
Underwriters [Member]
Stock Issued During Period, Shares, New Issues (in shares)		714,190
Public Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	4,762,000
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.001
Shares Issued, Price Per Share (in dollars per share)	$ 2.10
Underwriters, Additional Common Shares Authorized to Purchase (in shares)			714,190
Proceeds from Issuance of Common Stock	$ 10,300