Note 15 Segment and Geographic Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Net Revenues	$ 85,901	$ 68,461	$ 157,087	$ 149,318
Power Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	59,720	48,203	111,386	107,785
Integrated Circuits [Member]
Segment Reporting Information [Line Items]
Net Revenues	20,945	15,100	34,600	30,699
System and RF Power Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,236	5,158	11,101	10,834
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	22,526	20,241	44,084	45,163
France [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,329	1,125	2,632	2,698
Germany [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	9,509	7,446	17,162	16,603
Italy [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,021	905	1,994	1,931
Sweden [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,288	1,265	2,668	2,425
Switzerland [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,077	638	2,114	1,651
UNITED KINGDOM [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,411	6,429	10,747	13,553
China [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	20,267	10,586	34,941	23,970
Japan [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,701	1,717	3,406	3,545
Korea [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,440	2,082	7,304	4,325
Malaysia [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	920	1,146	1,623	2,449
Singapore [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	3,151	2,509	5,744	5,154
India [Member] | Rest Of World [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,199	1,470	2,547	3,272
Other Geographic Regions [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	6,945	6,419	13,182	13,470
Other Geographic Regions [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	2,590	2,572	4,089	5,151
Other Geographic Regions [Member] | Rest Of World [Member]
Segment Reporting Information [Line Items]
Net Revenues	$ 1,527	$ 1,911	$ 2,850	$ 3,958