Note 17 - Employee and Non-employee Stock Options - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Outstanding, shares (in shares)	9,182	10,000
Granted, shares (in shares)	0	0
Exercised, shares (in shares)	(1,682)	(818)
Forfeited, shares (in shares)
Repurchased, shares (in shares)	0	0
Outstanding, shares (in shares)	7,500	9,182	10,000
Exercisable, shares (in shares)	7,500
Outstanding, weighted average exercise price per share (in dollars per share)	$ 10.03	$ 10.08
Granted, weighted average exercise price per share (in dollars per share)	0	0
Exercised, weighted average exercise price per share (in dollars per share)	10.56	10.56
Forfeited, weighted average exercise price per share (in dollars per share)
Repurchased, weighted average exercise price per share (in dollars per share)	0	0
Outstanding, weighted average exercise price per share (in dollars per share)	9.91	$ 10.03	$ 10.08
Exercisable, weighted average exercise price per share (in dollars per share)	$ 9.91
Outstanding, weighted average remaining life (Year)	4 years 25 days	5 years 47 days	6 years 54 days
Exercisable, weighted average remaining life (Year)	4 years 25 days
Outstanding, aggregate intrinsic value	$ 152,075	$ 140,193	$ 101,000
Exercisable, aggregate intrinsic value	$ 152,075