Note 11 - Employee Equity Incentive Plans (Tables)

3 Months Ended

Jun. 30, 2015

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	2015		2014
	(unaudited)
Cost of goods sold	$	122	$	108
Research, development and engineering (1)		460		189
Selling, general and administrative expenses		406		384
Stock-based compensation effect in income before taxes		988		681
Provision for income taxes (2)		346		238
Net stock-based compensation effects in net income	$	642	$	443

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

	Stock Options (1)					Purchase Plan
	Three Months					Three Months
	Ended June 30,					Ended June 30,
	2015			2014		2015			2014
	(unaudited)					(unaudited)
Weighted average estimated fair value of grant per share	$	6.32		$	na	$	3.15		$	2.90
Risk-free interest rate		2.0	%		na		0.1	%		0.1	%
Expected term in years		6.75			na		1.00			0.50
Volatility		50.7	%		na		33.7	%		34.5	%
Dividend yield		1.01	%		na		1.11	%		1.06	%

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

				Weighted Average
	Number of			Exercise Price		Intrinsic Value (000) (1)
	Shares			Per Share
				(unaudited)
Balance at March 31, 2015		4,942,511		$	10.37
Options granted		293,000		$	13.37
Options exercised		(211,876	)	$	9.30	$	1,040
Options cancelled		(2,500	)	$	12.13
Options expired		(432,788	)	$	14.70
Balance at June 30, 2015		4,588,347		$	10.20
Exercisable at June 30, 2015		3,387,597		$	9.73
Exercisable at March 31, 2015		3,942,261		$	10.20