Note 5 - Fair Value of Financial Instruments (Details Textual)	6 Months Ended
	Sep. 30, 2022
Available for Sale Debt Securitites, Percent of Total Assets	76.00%
Number of Other-than-temporarily Impaired Available-for-sale Securities	0
Number of Other-than-temporarily Impaired Marketable Securities	0
Minimum [Member]
Available for Sale Debt Securities, Remaining Maturity (Week)	98 days
Maximum [Member]
Available for Sale Debt Securities, Remaining Maturity (Week)	79 months