Note 11 - Employee Equity Incentive Plans - Stock-based Compensation in Income Tax Provision (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Cost of Sales [Member]
Stock-based Compensation Effect in Income before Taxes		$ 96	$ 124	$ 196	$ 246
Research and Development Expense [Member]
Stock-based Compensation Effect in Income before Taxes		283	330	586	791	[1]
Selling, General and Administrative Expenses [Member]
Stock-based Compensation Effect in Income before Taxes		495	497	947	903
Stock-based Compensation Effect in Income before Taxes		874	951	1,729	1,940
Provision for income tax	[2]	350	333	692	679
Net stock-based compensation effects in net income		$ 524	$ 618	$ 1,037	$ 1,261

[1] Includes acquisition related compensation expenses of $249,000 during the six months ended September 30, 2015.

[2] Calculated at the U.S. statutory income tax rate of 40% in fiscal 2017 and 35% in fiscal 2016.