Note 11 - Employee Equity Incentive Plans (Tables)

3 Months Ended

Jun. 30, 2016

Notes Tables

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

	Three Months Ended June 30,
Statement of Operations Classifications	2016		2015
	(unaudited)
Cost of goods sold	$	100	$	122
Research, development and engineering (1)		303		460
Selling, general and administrative expenses		452		406
Stock-based compensation effect in income before taxes		855		988
Provision for income taxes (2)		342		346
Net stock-based compensation effects in net income	$	513	$	642

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

	Stock Options						Purchase Plan
	Three Months Ended June 30,						Three Months Ended June 30,
	2016			2015			2016			2015
	(unaudited)						(unaudited)
Weighted average estimated fair value of grant per share	$	3.96		$	6.32		$	3.94		$	3.15
Risk-free interest rate		1.4	%		2.0	%		0.26	%		0.1	%
Expected term in years		6.41			6.75			1.00			1.00
Volatility		41.0	%		50.7	%		42.9	%		33.7	%
Dividend yield		1.41	%		1.01	%		1.42	%		1.11	%

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

				Weighted Average
	Number of			Exercise Price		Intrinsic Value
	Shares			Per Share		(000) (1)
				(unaudited)
Balance at March 31, 2016		5,234,397		$	10.40
Options granted		222,000		$	10.97
Options exercised		(27,897	)	$	6.53	$	130
Options expired		(5,000	)	$	9.73
Balance at June 30, 2016		5,423,500		$	10.44
Exercisable at June 30, 2016		3,684,916		$	10.03
Exercisable at March 31, 2016		3,619,563		$	9.93