Note 6 - Other Assets (Details Textual) - USD ($)	3 Months Ended	6 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2016
Powersem GmbH [Member]
Equity Method Investments	$ 2,600,000		$ 2,600,000		$ 2,500,000
EB Tech Ltd [Member]
Equity Method Investments	2,700,000		2,700,000		2,700,000
ATEC [Member]
Equity Method Investments	5,900,000		5,900,000		5,700,000
Other than Temporary Impairment Losses, Investments	0	$ 454,000	151,000	$ 454,000
Equity Method Investments	11,457,000		11,457,000		$ 10,977,000
Cost Method Investments	$ 2,000,000		2,000,000
Equity Method Investment, Other than Temporary Impairment			0
Cost-method Investments, Other than Temporary Impairment			$ 0

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
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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