Note 7 - Stock Repurchase Program - Schedule of Stock Purchases (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended														12 Months Ended	36 Months Ended
	Apr. 30, 2019		Apr. 30, 2018		Apr. 30, 2019	[1]	Jan. 31, 2019	[1]	Oct. 31, 2018	[1]	Jul. 31, 2018	[1]	Apr. 30, 2018	[1]	Jan. 31, 2018	[1]	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Apr. 30, 2019		Dec. 31, 2016
Approximate Dollar Value of Shares That May Yet Be Purchased Under the Plan or Programs	$ 94	[1]	$ 281	[1]	$ 94		$ 317		$ 381		$ 525		$ 281		$ 326		$ 465	$ 468	$ 468	$ 94	[1]	$ 500
Stock repurchase (in shares)					580,705		186,727		480,805		25,277		178,526		536,058		8,607		130,346	2,127,051
Average Price Paid per Share (in dollars per share)					$ 0.38		$ 0.34		$ 0.30		$ 0.26		$ 0.25		$ 0.26		$ 0.30		$ 0.25	$ 0.31
Number of Shares Purchased as Part of Publicly Announced Plans or Programs (in shares)					580,705		186,727		480,805		25,277		178,526		536,058		8,607		130,346	2,127,051
Number of Shares Purchased (in shares)					580,705		186,727		480,805		25,277		178,526		536,058		8,607		130,346	2,127,051
Increase in program authorization, Approximate Dollar Value of Shares That May Yet Be Purchased Under the Plan or Programs	$ 1,569	[2]	$ 531	[3]

[1] These shares of common stock purchased were purchased through private transactions

[2] Board of Directors increased program authorization from $750 to $2,225

[3] Board of Directors increased program authorization from $500 to $750