Note 6 - Other Assets (Details Textual) - USD ($)	3 Months Ended	9 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2016
Other than Temporary Impairment Losses, Investments	$ 0	$ 0	$ 151,000	$ 454,000
Equity Method Investments	11,554,000		11,554,000		$ 10,977,000
Cost Method Investments	1,900,000		1,900,000
Equity Method Investment, Other than Temporary Impairment			0
Cost-method Investments, Other than Temporary Impairment			0
Powersem GmbH [Member]
Equity Method Investments	2,500,000		2,500,000		2,500,000
EB Tech Ltd [Member]
Equity Method Investments	2,700,000		2,700,000		2,700,000
ATEC [Member]
Equity Method Investments	$ 6,400,000		$ 6,400,000		$ 5,700,000

Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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