Note 14 Segment and Geographic Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting Information [Line Items]
Net Revenues	$ 280,014	$ 368,004	$ 363,273
Net Income (Loss)	7,648	30,306	36,647
Property, Plant and Equipment, Net	51,995	56,071
Power Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	200,907	277,718	252,892
Integrated Circuits [Member]
Segment Reporting Information [Line Items]
Net Revenues	57,993	63,597	83,225
System and RF Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	21,114	26,689	27,156
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	84,789	103,122	102,190
Property, Plant and Equipment, Net	29,308	29,760
France [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,235	7,433	7,071
Germany [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	20,711	24,098
Germany [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	32,287	47,499	42,385
Italy [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	4,087	6,274	6,054
Sweden [Member]
Segment Reporting Information [Line Items]
Net Revenues	4,588	5,297	4,922
United Kingdom [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	1,971	2,192
United Kingdom [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	23,853	31,131	28,729
China [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	44,504	61,723	68,794
Japan [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	6,514	9,070	11,737
Korea [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	8,311	11,988	9,464
Malaysia [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	4,606	4,744	4,953
Singapore [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	9,994	10,332	10,481
Taiwan [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	3,981	6,797	9,372
India [Member] | Rest of the World [Member]
Segment Reporting Information [Line Items]
Net Revenues	6,080	8,198	8,319
Other Geographic Regions [Member]
Segment Reporting Information [Line Items]
Property, Plant and Equipment, Net	5	21
Other Geographic Regions [Member] | Europe and the Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	28,518	40,927	37,673
Other Geographic Regions [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,494	6,483	5,196
Other Geographic Regions [Member] | Rest of the World [Member]
Segment Reporting Information [Line Items]
Net Revenues	7,173	6,986	5,933
Foreign [Member]
Segment Reporting Information [Line Items]
Net Revenues	134,962	175,667	163,277
Net Income (Loss)	7,774	22,487	16,829
Domestic [Member]
Segment Reporting Information [Line Items]
Net Revenues	145,052	192,337	199,996
Net Income (Loss)	$ (126)	$ 7,819	$ 19,818