Note 10 - Net Income (Loss) Per Common Share (Details Textual) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	1,900,000	2,500,000
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	63,000	3.0
Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	286,000	146,000