Note 10 - Share-based Compensation - Shares Authorized, Available for Future Grant and Outstanding Under Each Plan (Details) - shares	Dec. 31, 2018	Mar. 31, 2018
Authorized (in shares)	1,650,000
Available (in shares)	1,297,422
Outstanding (in shares)	629,375
Restricted Stock Units (RSUs) [Member]
Outstanding (in shares)	50,975	39,675
The 2016 Plan [Member] \| Restricted Stock Units (RSUs) [Member]
Authorized (in shares)	1,300,000
Available (in shares)	1,113,022
Outstanding (in shares)	170,975
2014 Directors Plan [Member]
Authorized (in shares)	350,000
Available (in shares)	184,400
Outstanding (in shares)	12,000
The 2005 Plan [Member]
Authorized (in shares)
Available (in shares)	0
Outstanding (in shares)	434,400
2004 Directors Plan [Member]
Authorized (in shares)
Available (in shares)	0
Outstanding (in shares)	12,000

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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