Note 4 - Marketable Securities - Gross Unrealized Losses and Fair Value of Investments (Details) - USD ($)	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair market value, less than 12 months	$ 33,503,369	$ 3,003,606
Gross unrealized losses, less than 12 months	(247,149)	(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	33,503,369	5,603,476
Total gross unrealized losses	(247,149)	(10,824)
Corporate Bond Securities [Member]
Fair market value, less than 12 months	32,198,766	3,003,606
Gross unrealized losses, less than 12 months	(246,935)	(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	32,198,766	5,603,476
Total gross unrealized losses	(246,935)	(10,824)
Municipal Bonds [Member]
Fair market value, less than 12 months	1,304,603
Gross unrealized losses, less than 12 months	(214)
Fair market value, greater than 12 months
Gross unrealized losses, greater than 12 months
Total fair market value	1,304,603
Total gross unrealized losses	$ (214)