Note 5 - Other Assets (Details Textual) - USD ($)	3 Months Ended
Sep. 30, 2017	Mar. 31, 2017
Available-for-sale Debt Securities, Amortized Cost Basis	$ 9,100,000	$ 503,000
Equity Method Investments	12,551,000	11,589,000
Powersem GmbH [Member]
Equity Method Investments	2,800,000	2,500,000
EB Tech Ltd [Member]
Equity Method Investments	2,600,000	2,600,000
ATEC [Member]
Equity Method Investments	7,100,000	$ 6,500,000
Convertible Debt Securities [Member]
Payments to Acquire Available-for-sale Securities, Debt	$ 4,400,000
Available for sale Securities, Debt, Interest Rate	3.00%
Available for sale Securities, Debt, Term	3 years
Available for sale Securities, Debt, Convertible, Percentage of Interest	95.00%

The percent of interest in ownership that an available for sale debt security entitles the holder to.

No definition available.

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- Definition

The interest rate on available for sale debt securities.

+ References

No definition available.

+ Details

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- Definition

The term of available for sale debt securities.

+ References

No definition available.

+ Details

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- Definition

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: 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

+ Details

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Period Type:	instant

- Definition

The cash outflow to acquire debt securities classified as available-for-sale securities, because they are not classified as either held-to-maturity securities or trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26853-111562

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Period Type:	duration

- Details

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- Details

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- Details

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- Details

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