Note 11 - Employee Equity Incentive Plans - Allocated Share-based Compensation Expense (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Cost of Sales [Member]
Stock-based Compensation Effect in Income before Taxes		$ 125	$ 110	$ 371	$ 320
Research and Development Expense [Member]
Stock-based Compensation Effect in Income before Taxes	[1]	242	224	1,032	602
Selling, General and Administrative Expenses [Member]
Stock-based Compensation Effect in Income before Taxes		471	415	1,374	1,205
Stock-based Compensation Effect in Income before Taxes		838	749	2,777	2,127
Provision for income taxes	[2]	293	262	972	744
Net stock-based compensation effects in net income		$ 545	$ 487	$ 1,805	$ 1,383

[1] Includes acquisition-related compensation expenses of $249,000 during the nine months ended December 31, 2015.

[2] Calculated at the U.S. statutory federal income tax rate of 35% in fiscal 2016 and 2015.