Note 10 - Employee Equity Incentive Plans (Tables)

12 Months Ended

Mar. 31, 2016

Notes Tables

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

	Year Ended March 31,
Statement of Operations Classifications	2016		2015		2014
Cost of goods sold	$	488	$	433	$	457
Research, development and engineering (1)		1,272		814		978
Selling, general and administrative		1,832		1,620		1,350
Stock-based compensation effect on 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

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

	Stock Options									Purchase Plan
	Year Ended March 31,									Year Ended March 31,
	2016			2015			2014			2016			2015			2014
Weighted average estimated per share fair value of grant	$	4.83		$	5.54		$	5.31		$	3.33		$	2.90		$	2.75
Risk-free interest rate		1.8	%		1.8	%		1.8	%		0.1	%		0.1	%		0.1	%
Expected term in years		6.45			6.25			6.05			0.50			0.50			0.50
Volatility		44.9	%		52.2	%		54.9	%		39.8	%		36.9	%		37.0	%
Dividend yield (1)		1.2	%		1.0	%		1.0	%		1.1	%		1.1	%		0	%

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

Stock compensation activity under our equity incentive plans for fiscal 2016, 2015 and 2014 is summarized below:
	Shares Available			Options Outstanding						Weighted Average Exercise Price
	for Grant			Number of Shares (1)			Intrinsic Value (2)			per Share
								(000	)
Balances, March 31, 2013		451,713			5,327,473		$	4,273		$	10.04
New shares authorized (3)		2,000,000			-
Plan authorization expired		(47,963	)		-
Options granted		(515,000	)		515,000					$	10.63
Options exercised		-			(572,338	)	$	1,695		$	8.72
Options cancelled		24,000			(34,000	)				$	11.42
Options expired		17,500			(34,500	)				$	12.62
Balances, March 31, 2014		1,930,250			5,201,635		$	8,658		$	10.22
Options granted		(249,000	)		249,000					$	11.83
Options exercised		-			(339,374	)	$	1,310		$	8.62
Options cancelled		39,750			(94,250	)				$	11.46
Options expired		26,000			(74,500	)				$	11.17
Balances, March 31, 2015		1,747,000			4,942,511		$	10,831		$	10.37
Options granted		(1,124,000	)		1,124,000					$	11.72
Options exercised		-			(382,826	)	$	1,551		$	9.02
Options cancelled		14,500			(14,500	)				$	11.31
Options expired		-			(434,788	)				$	14.68
Balances, March 31, 2016		637,500			5,234,397		$	6,456		$	10.40

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

Options Outstanding									Options Exercisable
Exercise Price per Share			Number of Shares Outstanding		Weighted Average Contractual Life		Weighted Average Exercise Price per Share		Number of Shares Exercisable		Weighted Average Exercise Price per Share
$5.01	-	$7.75		819,897		2.6	$	6.63		819,897	$	6.63
$7.76	-	$10.00		1,223,500		4.8	$	9.33		1,017,750	$	9.29
$10.01	-	$12.50		2,448,000		6.6	$	11.42		1,331,916	$	11.52
$12.51	-	$13.37		743,000		6.1	$	12.96		450,000	$	12.69
$5.01	-	$13.37		5,234,397		5.5	$	10.40		3,619,563	$	9.93