Note 14 Segment and Geographic Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Net Revenues	$ 86,435	$ 85,901	$ 174,515	$ 157,087
Power Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	55,780	59,720	113,748	111,386
Integrated Circuits [Member]
Segment Reporting Information [Line Items]
Net Revenues	23,438	20,945	47,320	34,600
System and RF Power Semiconductors [Member]
Segment Reporting Information [Line Items]
Net Revenues	7,217	5,236	13,447	11,101
United States [Member]
Segment Reporting Information [Line Items]
Net Revenues	21,502	22,526	44,006	44,084
France [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,897	1,329	3,749	2,632
Germany [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	8,026	9,509	16,475	17,162
Italy [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	909	1,021	2,382	1,994
Russia [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	2,157	899	2,860	1,380
Sweden [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,309	1,288	2,594	2,668
Switzerland [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	853	1,077	1,671	2,114
United Kingdom [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,822	5,411	11,201	10,747
China [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	20,480	20,267	40,882	34,941
Japan [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	2,161	1,701	3,962	3,406
Korea [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,689	5,440	12,128	7,304
Malaysia [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,490	920	3,122	1,623
Singapore [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	2,913	3,151	6,070	5,744
India [Member] | Rest Of World [Member]
Segment Reporting Information [Line Items]
Net Revenues	1,380	1,199	2,629	2,547
Other Geographic Regions [Member] | Europe and Middle East [Member]
Segment Reporting Information [Line Items]
Net Revenues	5,957	6,046	12,223	11,802
Other Geographic Regions [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net Revenues	2,685	2,590	5,843	4,089
Other Geographic Regions [Member] | Rest Of World [Member]
Segment Reporting Information [Line Items]
Net Revenues	$ 1,205	$ 1,527	$ 2,718	$ 2,850