Note 11 - Employee Equity Incentive Plans (Tables)

9 Months Ended

Dec. 31, 2015

Notes Tables

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended December 31,				Nine Months Ended December 31,
Statement of Operations Classifications	2015		2014		2015		2014
	(unaudited)				(unaudited)
Cost of goods sold	$	125	$	110	$	371	$	320
Research, development and engineering expenses (1)		242		224		1,032		602
Selling, general and administrative expenses		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

Schedule of Employee Service Share Based Compensation Fair Value Assumptions and Methodology [Table Text Block]

	Stock Options (1)										Purchase Plan (2)
	Three Months Ended December 31,				Nine Months Ended December 31,						Nine Months Ended December 31,
	2015		2014		2015			2014			2015			2014
	(unaudited)				(unaudited)						(unaudited)
Weighted average estimated fair value of grant per share		na		na	$	4.83		$	5.54		$	3.54		$	2.90
Risk-free interest rate		na		na		1.8	%		1.8	%		0.1	%		0.1	%
Expected term in years		na		na		6.45			6.30			0.50			0.50
Volatility		na		na		44.9	%		52.2	%		48.2	%		36.9	%
Dividend yield		na		na		1.2	%		1.0	%		1.2	%		1.1	%

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

				Weighted Average
	Number of			Exercise Price		Intrinsic Value (1)
	Shares			Per Share
				(unaudited)			(000	)
Balance at March 31, 2015		4,942,511		$	10.37
Options granted		1,124,000		$	11.72
Options exercised		(369,826	)	$	9.11	$	1,484
Options cancelled		(2,500	)	$	12.13
Options expired		(434,788	)	$	14.68
Balance at December 31, 2015		5,259,397		$	10.39
Exercisable at December 31, 2015		3,499,063		$	9.88
Exercisable at March 31, 2015		3,942,261		$	10.20