Note 6 - Stock-based Compensation - Non-vested Stock to Directors (Details) - Non Employee Directors [Member] - Non-vested Stock Grants [Member]	9 Months Ended
Dec. 31, 2018 $ / shares shares
August 8, 2018 [Member]
Fair Value Per Share (in dollars per share) \| $ / shares	$ 5.43
Number of Shares (in shares) \| shares	28,000
August 9 2017 [Member]
Fair Value Per Share (in dollars per share) \| $ / shares	$ 5.50
Number of Shares (in shares) \| shares	28,000
August 10, 2016 [Member]
Fair Value Per Share (in dollars per share) \| $ / shares	$ 10.08
Number of Shares (in shares) \| shares	28,000
August 12, 2015 [Member]
Fair Value Per Share (in dollars per share) \| $ / shares	$ 8.20
Number of Shares (in shares) \| shares	28,000

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration