Note 12 - Segment and Geographic Information - Segment and Geographic Information (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
UNITED STATES
Net Revenues	19,275	20,185	38,888	39,686
FRANCE
Net Revenues	2,010	2,121	3,945	5,571
GERMANY
Net Revenues	10,922	8,960	20,980	17,559
ITALY
Net Revenues	1,195	915	2,173	1,991
NETHERLANDS
Net Revenues	1,420	941	2,816	2,081
UNITED KINGDOM
Net Revenues	4,687	3,209	8,490	6,836
Other Europe and the Middle East Regions [Member]
Net Revenues	6,585	5,429	12,439	11,382
CHINA
Net Revenues	24,914	21,218	48,733	43,858
JAPAN
Net Revenues	2,146	1,708	4,265	3,426
MALAYSIA [Member]
Net Revenues	1,233	1,288	2,057	2,092
SINGAPORE
Net Revenues	3,102	3,577	6,121	6,584
KOREA, REPUBLIC OF
Net Revenues	5,301	4,353	11,114	9,048
THAILAND
Net Revenues	937	1,040	1,744	1,851
Other Asia Pacific Regions [Member]
Net Revenues	1,828	1,403	3,020	3,150
INDIA
Net Revenues	818	1,207	1,858	2,107
Other Rest of the World [Member]
Net Revenues	$ 1,311	$ 1,075	$ 2,583	$ 2,045