Note 5 - Marketable Securities - Gross Unrealized Losses and Fair Value of Investments (Details) - USD ($)	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Mar. 31, 2016
Fair market value, less than 12 months	$ 31,460,549	$ 3,003,606
Gross unrealized losses, less than 12 months	(336,187)	(6,703)
Fair market value, greater than 12 months		2,599,870
Gross unrealized losses, greater than 12 months		(4,121)
Total Fair Market Value	31,460,549	5,603,476
Total Gross Unrealized Losses	(336,187)	(10,824)
Corporate Bond Securities [Member]
Fair market value, less than 12 months	30,147,097	3,003,606
Gross unrealized losses, less than 12 months	(334,944)	(6,703)
Fair market value, greater than 12 months		2,599,870
Gross unrealized losses, greater than 12 months		(4,121)
Total Fair Market Value	30,147,097	5,603,476
Total Gross Unrealized Losses	(334,944)	(10,824)
Municipal Bonds [Member]
Fair market value, less than 12 months	1,313,452
Gross unrealized losses, less than 12 months	(1,243)
Fair market value, greater than 12 months
Gross unrealized losses, greater than 12 months
Total Fair Market Value	1,313,452
Total Gross Unrealized Losses	$ (1,243)