Note 12 - Segment and Geographic Information - Revenue by Product Line (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Revenues	$ 87,684	$ 78,629	$ 171,226	$ 159,267
Power Semiconductors [Member]
Net Revenues	62,027	53,537	119,655	110,016
Integrated Circuits [Member]
Net Revenues	21,295	20,553	42,467	40,935
Systems and RF Power Semiconductors [Member]
Net Revenues	$ 4,362	$ 4,539	$ 9,104	$ 8,316