Note 10 - Shareholders' Equity - Information About Stock Options (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 1.58
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 3.90
Options Outstanding, Options (in shares) | shares	1,022,913
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 2.69
Options Outstanding, Weighted Average Remaining Contract Life (Year)	3 years 76 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 1,047,000
Options Exercisable, Options (in shares) | shares	406,835
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 2.30
Options Exercisable, Weighted Average Remaining Contract Life (Year)	2 years 208 days
Options Exercisable, Aggregate Intrinsic Value | $	$ 573,000