Note 11 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	1 Months Ended
	Oct. 31, 2018	Mar. 31, 2020	Dec. 31, 2019
Common Stock, Shares Authorized (in shares)		160,000	160,000
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.0013	$ 0.0013
Preferred Stock, Shares Authorized (in shares)		20,000	20,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001	$ 0.001
Replacement Shelf Registration	$ 250
Common Stock Sales Agreement with Agent, Maximum Aggregate Offering Price	$ 75