Note 5 - Fair Value of Financial Instruments (Tables)

3 Months Ended

Jun. 30, 2019

Notes Tables

Investments Classified by Contractual Maturity Date [Table Text Block]

Total		<1 Year		1–3 Years		3–5 Years
$	61,611,878	$	2,999,689	$	36,251,115	$	22,361,074

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

	As of June 30, 2019						As of March 31, 2019
	Level 1		Level 2		Total		Level 1		Level 2		Total
Money market funds	$	12,774,255	$	-	$	12,774,255	$	6,703,809	$	-	$	6,703,809
Corporate bonds		-		61,611,878		61,611,878		-		67,413,454		67,413,454
Total	$	12,774,255	$	61,611,878	$	74,386,133	$	6,703,809	$	67,413,454	$	74,117,263

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

	As of June 30, 2019									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	$	12,774,255	$	-	$	-		$	12,774,255	$	6,703,809	$	-	$	-		$	6,703,809
Corporate bonds		60,988,047		691,342		(67,511	)		61,611,878		67,519,350		315,902		(421,798	)		67,413,454
Total	$	73,762,302	$	691,342	$	(67,511	)	$	74,386,133	$	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 June 30, 2019
Corporate bonds	$	-	$	-	$	24,235,229	$	(67,511	)	$	24,235,229	$	(67,511	)
Total	$	-	$	-	$	24,235,229	$	(67,511	)	$	24,235,229	$	(67,511	)
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	)