Note 10 - Stockholders' Equity - Summary of Information Concerning Outstanding and Exercisable Stock Options (Details)	6 Months Ended
	Jun. 30, 2020 $ / shares shares
Number of outstanding (in shares)	5,875,750
Number of exercisable (in shares)	3,120,450
Range 1 [Member]
0.Range of exercise prices per share (in dollars per share) | $ / shares	$ 0.33
Number of outstanding (in shares)	2,745,000
Number of exercisable (in shares)	60,000
Expiry date	Jun. 30, 2025
Range 2 [Member]
0.Range of exercise prices per share (in dollars per share) | $ / shares	$ 0.42
Number of outstanding (in shares)	620,000
Number of exercisable (in shares)	620,000
Expiry date	Dec. 20, 2021
Range 3 [Member]
0.Range of exercise prices per share (in dollars per share) | $ / shares	$ 0.42
Number of outstanding (in shares)	522,750
Number of exercisable (in shares)	452,450
Expiry date	Nov. 08, 2022
Range 4 [Member]
0.Range of exercise prices per share (in dollars per share) | $ / shares	$ 0.42
Number of outstanding (in shares)	713,000
Number of exercisable (in shares)	713,000
Expiry date	Jun. 04, 2023
Range 5 [Member]
0.Range of exercise prices per share (in dollars per share) | $ / shares	$ 0.50
Number of outstanding (in shares)	1,275,000
Number of exercisable (in shares)	1,275,000
Expiry date	Jun. 04, 2023