Note 8 - Concentrations - Revenue by Major Customers (Details) - Sales Revenue, Net [Member] - Customer Concentration Risk [Member]	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Customer A [Member]
Percentage of concentration	19.00%	22.00%	23.00%
Customer B [Member]
Percentage of concentration	18.00%	20.00%	20.00%

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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