Note 7 - Shareholders' Equity (Details Textual) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 1998	Mar. 31, 2018	Mar. 31, 2017	Jan. 22, 2018	May 08, 2017	May 09, 2016	Aug. 01, 2011	Nov. 01, 2010	Oct. 31, 2008	Nov. 08, 2006
Preferred Stock, Shares Issued, Total	250,000	3,000	3,000
Preferred Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001	$ 0.001
Shares Issued, Price Per Share	$ 4
Payments of Stock Issuance Costs	$ 112,187
Convertible Preferred Stock, Shares Issued upon Conversion	4.05
Preferred Stock, Liquidation Preference Per Share	$ 4	$ 4	$ 4
Preferred Stock, Shares Outstanding, Ending Balance		3,000	3,000
Stock Repurchase Program, Authorized Amount							$ 20,000,000	$ 20	$ 20,000,000	$ 20,000,000
Treasury Stock, Shares, Acquired		0	0
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 10,200,000
Dividends Payable, Amount Per Share				$ 0.25	$ 0.20	$ 0.19
Convertible Preferred Stock [Member]
Preferred Stock, Shares Outstanding, Ending Balance		2,500	2,500