Note 13 - Subsequent Event (Details Textual)	Oct. 12, 2020 $ / shares shares	Sep. 28, 2020	Sep. 15, 2020	Sep. 30, 2020 $ / shares	Dec. 31, 2019 $ / shares
Common Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.01	$ 0.01
Stock Split From [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio		3	3
Stock Split To [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio		2	2
Common Class A [Member] | Subsequent Event [Member]
Additional Share Issued for Every Two Shares of Common Stock (in shares) | shares	1
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.01
Common Class B [Member] | Subsequent Event [Member]
Additional Share Issued for Every Two Shares of Common Stock (in shares) | shares	1
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.01