Note 10 - Share-based Compensation - Summary of the Weighted-average Characteristics of Outstanding Stock Options (Details)	12 Months Ended
Mar. 31, 2020 $ / shares shares
Outstanding Options Number of Shares (in shares) \| shares	318,300
Outstanding Options Remaining Life (Year)	3 years
Outstanding Options Weighted Average Price (in dollars per share)	$ 4.08
Exercisable Options Number of Shares (in shares) \| shares	280,800
Exercisable Options Weighted Average Price (in dollars per share)	$ 2.29
Range 01 [Member]
Lower Range of Exercise (in dollars per share)	2.11
Upper Range of Exercise (in dollars per share)	$ 3.70
Outstanding Options Number of Shares (in shares) \| shares	93,400
Outstanding Options Remaining Life (Year)	5 years 255 days
Outstanding Options Weighted Average Price (in dollars per share)	$ 3.19
Exercisable Options Number of Shares (in shares) \| shares	55,900
Exercisable Options Weighted Average Price (in dollars per share)	$ 3.70
Range 02 [Member]
Lower Range of Exercise (in dollars per share)	3.71
Upper Range of Exercise (in dollars per share)	$ 3.95
Outstanding Options Number of Shares (in shares) \| shares	146,400
Outstanding Options Remaining Life (Year)	1 year 146 days
Outstanding Options Weighted Average Price (in dollars per share)	$ 3.82
Exercisable Options Number of Shares (in shares) \| shares	146,400
Exercisable Options Weighted Average Price (in dollars per share)	$ 1.41
Range 03 [Member]
Lower Range of Exercise (in dollars per share)	3.96
Upper Range of Exercise (in dollars per share)	$ 5.73
Outstanding Options Number of Shares (in shares) \| shares	31,000
Outstanding Options Remaining Life (Year)	3 years 73 days
Outstanding Options Weighted Average Price (in dollars per share)	$ 5.27
Exercisable Options Number of Shares (in shares) \| shares	31,000
Exercisable Options Weighted Average Price (in dollars per share)	$ 3.23
Range 04 [Member]
Lower Range of Exercise (in dollars per share)	5.74
Upper Range of Exercise (in dollars per share)	$ 5.91
Outstanding Options Number of Shares (in shares) \| shares	47,500
Outstanding Options Remaining Life (Year)	2 years 255 days
Outstanding Options Weighted Average Price (in dollars per share)	$ 5.85
Exercisable Options Number of Shares (in shares) \| shares	47,500
Exercisable Options Weighted Average Price (in dollars per share)	$ 2.71

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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