Note 10 - Employee Equity Incentive Plans (Tables)

12 Months Ended

Mar. 31, 2017

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	2017		2016		2015
Cost of goods sold	$	362	$	488	$	433
Research, development and engineering (1)		1,144		1,272		814
Selling, general and administrative		1,932		1,832		1,620
Stock-based compensation effect in income before income tax provision		3,438		3,592		2,867
Provision for income tax		694		660		1,009
Net stock-based compensation effects on net income	$	2,744	$	2,932	$	1,858

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,
	2017			2016			2015			2017			2016			2015
Weighted average estimated fair value of grant per share	$	4.48		$	4.83		$	5.54		$	3.28		$	3.33		$	2.90
Risk-free interest rate		1.6	%		1.8	%		1.8	%		0.4	%		0.1	%		0.1	%
Expected term in years		6.41			6.45			6.25			0.75			0.50			0.50
Volatility		40.6	%		44.9	%		52.2	%		37.5	%		39.8	%		36.9	%
Dividend yield		0.4	%		1.2	%		1.0	%		0.7	%		1.1	%		1.1	%

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

Stock compensation activities under our equity incentive plans for fiscal 2017, 2016 and 2015 were as follows:
				Options Outstanding
	Shares Available for  Grant			Number of Shares (1)			Intrinsic Value (2)		Weighted  Average  Exercise Price  per Share
								(000)
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
New shares authorized (3)		2,000,000
Options granted		(746,000	)		746,000				$	11.06
Options exercised		-			(859,852	)	$	3,112	$	9.10
Options cancelled		7,500			(7,500	)			$	13.37
Options expired		22,500			(27,500	)			$	11.81
Balances, March 31, 2017		1,921,500			5,085,545		$	19,570	$	10.70

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		576,500		1.6	$	6.66		576,500	$	6.66
$	7.76	-	10.00		843,295		4.7	$	9.30		783,545	$	9.30
$	10.01	-	12.50		2,890,750		6.9	$	11.31		1,417,000	$	11.51
$	12.51	-	14.50		775,000		5.4	$	12.95		523,250	$	12.78
$	5.01	-	14.50		5,085,545		5.7	$	10.70		3,300,295	$	10.34

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