Note 10 - Employee Equity Incentive Plans - Allocated Share-based Compensation Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Cost of Sales [Member]
Stock-based Compensation Effect in Income before Taxes		$ 488	$ 433	$ 457
Research and Development Expense [Member]
Stock-based Compensation Effect in Income before Taxes	[1]	1,272	814	978
Selling, General and Administrative Expenses [Member]
Stock-based Compensation Effect in Income before Taxes		1,832	1,620	1,350
Stock-based Compensation Effect in Income before Taxes		3,592	2,867	2,785
Benefit from income taxes		660	1,009	1,071
Net stock-based compensation effects on net income		$ 2,932	$ 1,858	$ 1,714

[1] Includes acquisition-related compensation expenses of $249,000 during fiscal 2016.