Note 6 - Summary of Stock Options and Warrants (Details) - $ / shares	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Option Shares Reserved [Member]
Options Outstanding (in shares)	147,230	151,230	155,230	158,230
Granted (in shares)	(4,000)	(4,000)	(4,000)
Exercised (in shares)
Terminated (in shares)			(1,000)
Employee Stock Option [Member]
Options Outstanding (in shares)	21,000	35,090	38,000	49,000
Weighted Average Option Exercise Price (in dollars per share)	$ 52.85	$ 33.51	$ 31.78	$ 30.27
Granted (in shares)	4,000	4,000	4,000
Granted (in dollars per share)	$ 56.76	$ 67.69	$ 49.86
Exercised (in shares)	(18,090)	(6,910)	(14,000)
Exercised (in dollars per share)	$ 16.19	$ 43.81	$ 29.77
Terminated (in shares)			(1,000)
Terminated (in dollars per share)			$ 58.27
Warrants [Member]
Options Outstanding (in shares)	0	0	2,000	4,000
Weighted Average Option Exercise Price (in dollars per share)			$ 37.38	$ 29.69
Granted (in shares)
Granted (in dollars per share)
Exercised (in shares)
Exercised (in dollars per share)
Terminated (in shares)		(2,000)	(2,000)
Terminated (in dollars per share)		$ 37.38	$ 21.99