Note 3 - Fair Value of Financial Instruments (Tables)

12 Months Ended

Mar. 31, 2020

Notes Tables

Investments Classified by Contractual Maturity Date [Table Text Block]

Total		<1 Year		1–3 Years		3–5 Years
$	70,594,742	$	26,988,247	$	28,683,823	$	14,922,672

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

	As of March 31, 2020						As of March 31, 2019
	Level 1		Level 2		Total		Level 1		Level 2		Total
Money market funds	$	7,903,433	$	-	$	7,903,433	$	6,703,809	$	-	$	6,703,809
Corporate bonds		-		62,691,309		62,691,309		-		67,413,454		67,413,454
Total	$	7,903,433	$	62,691,309	$	70,594,742	$	6,703,809	$	67,413,454	$	74,117,263

Schedule of Available-for-sale Securities Reconciliation [Table Text Block]

	As of March 31, 2020									As of March 31, 2019
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Money market funds	$	7,903,433	$	-	$	-		$	7,903,433	$	6,703,809	$	-	$	-		$	6,703,809
Corporate bonds		62,030,120		752,621		(91,432	)		62,691,309		67,519,350		315,902		(421,798	)		67,413,454
Total	$	69,933,553	$	752,621	$	(91,432	)	$	70,594,742	$	74,223,159	$	315,902	$	(421,798	)	$	74,117,263

Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block]

	Less Than 12 Months					12 Months or Greater					Total
	Estimated Fair Value		Gross Unrealized Holding Losses			Estimated Fair Value		Gross Unrealized Holding Losses			Estimated Fair Value		Gross Unrealized Holding Losses
As of March 31, 2020
Corporate bonds	$	19,525,169	$	(91,432	)	$	-	$	-		$	19,525,169	$	(91,432	)
Total	$	19,525,169	$	(91,432	)	$	-	$	-		$	19,525,169	$	(91,432	)
As of March 31, 2019
Corporate bonds	$	-	$	-		$	51,413,428	$	(421,798	)	$	51,413,428	$	(421,798	)
Total	$	-	$	-		$	51,413,428	$	(421,798	)	$	51,413,428	$	(421,798	)