Note 15 Segment and Geographic Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Net Revenues	$ 336,330	$ 280,014	$ 368,004
Net Income (Loss)	6,046	7,648	30,306
Property, Plant and Equipment, Net	50,569	51,995
Power Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	222,813	200,907	277,718
Integrated Circuits [Member]
Segment Reporting Information [Line Items]
Net Revenues	91,189	57,993	63,597
System and RF Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	22,328	21,114	26,689
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	89,734	84,789	103,122
Property, Plant and Equipment, Net	27,287	29,308
France [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,554	5,235	7,433
Germany [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	21,697	20,711
Germany [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	34,423	32,287	47,499
Italy [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	4,506	4,087	6,274
Sweden | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	4,938	4,588	5,297
Switzerland [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	3,714	3,216	4,606
United Kingdom [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	1,579	1,971
United Kingdom [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	19,524	23,853	31,131
China [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	83,849	44,504	61,723
Japan [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	6,740	6,514	9,070
Korea [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	19,466	8,311	11,988
Malaysia [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	3,766	4,606	4,744
Singapore [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	11,838	9,994	10,332
Taiwan [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	2,962	3,981	6,797
Thailand [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	3,031	2,529	2,587
India [Member] | Rest of the World [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,245	6,080	8,198
Other Geographic Regions [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	6	5
Other Geographic Regions [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	26,390	25,302	36,321
Other Geographic Regions [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	3,989	2,965	3,896
Other Geographic Regions [Member] | Rest of the World [Member]
Segment Reporting Information [Line Items]
Net Revenues	6,661	7,173	6,986
Foreign [Member]
Segment Reporting Information [Line Items]
Net Revenues	167,428	134,962	175,667
Net Income (Loss)	4,087	7,774	22,487
Domestic [Member]
Segment Reporting Information [Line Items]
Net Revenues	168,902	145,052	192,337
Net Income (Loss)	$ 1,959	$ (126)	$ 7,819