Note 1 - Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Accounts Receivable, Allowance for Credit Loss, Current	$ 39,000	$ 35,000
Inventory Valuation Reserves, Ending Balance	54,000	58,000
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	$ 0	$ 0	$ 0
Cost of Goods and Service Benchmark [Member] \| Supplier Concentration Risk [Member]
Number of Suppliers	4	4
Concentration Risk, Percentage	50.00%	50.00%
Building [Member]
Property, Plant and Equipment, Useful Life	30 years
Furniture, Fixtures, Equipment and Computer Software [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Furniture, Fixtures, Equipment and Computer Software [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years

Represents the number of major suppliers of the Company.

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Amount of allowance for credit loss on accounts receivable, classified as current.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Amount of valuation reserve for inventory.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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