STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Sep. 30, 2013

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation Expense Included in Statements of Operations [Table Text Block]

The following table summarizes the amount of stock-based compensation included in the condensed consolidated statements of operations:

	Three Months Ended						Six Months Ended
	September 30,						September 30,
(in thousands)	2013			2012			2013			2012
Cost of revenues	$	638		$	526		$	1,173		$	1,122
Research, development and engineering	1,652			1,256			3,020			2,380
Selling, general and administrative	3,675			3,080			6,760			5,980
Stock-based compensation included in operating expenses	5,327			4,336			9,780			8,360
Total stock-based compensation	5,965			4,862			10,953			9,482
Income tax benefit	(1,838		)	(1,532		)	(3,275		)	(2,914		)
Total stock-based compensation, net of tax	$	4,127		$	3,330		$	7,678		$	6,568

Summary of Stock Option Activity [Table Text Block]

The following is a summary of the Company’s stock option activity during the six months ended September 30, 2013:

	Options Outstanding
	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value
	(in thousands)				(in years)	(in thousands)
Outstanding at March 31, 2013	2,415		$	27.96
Options granted	176		$	45.98
Options exercised	(667	)	$	24.09
Options forfeited or expired	(10	)	$	32.74
Outstanding at September 30, 2013	1,914		$	30.94	4.2	$	29,739
Vested and expected to vest at September 30, 2013	1,872		$	30.76	4.2	$	29,419
Exercisable at September 30, 2013	1,275		$	27.85	3.4	$	23,735

Summary of Restricted Stock Activity [Table Text Block]

Restricted stock consists of awards of restricted stock and restricted stock units ("RSUs"). The following is a summary of the Company’s restricted stock activity during the six months ended September 30, 2013:

	Number of Shares		Weighted Average Grant Date Fair Value
	(in thousands)
Non-vested at March 31, 2013	1,025		$	33.34
Restricted stock granted	541		$	46.10
Restricted stock vested	(274	)	$	32.61
Restricted stock forfeited	(31	)	$	36.86
Non-vested at September 30, 2013	1,261		$	38.88

Valuation Assumptions [Table Text Block]

At the date of grant, the Company estimated the fair value of each stock option grant and purchase right granted under the ESPP using the following weighted average assumptions:

	Three Months Ended						Six Months Ended
	September 30,						September 30,
Employee Stock Options	2013			2012			2013			2012
Expected volatility	30.7		%	43.5		%	33.5		%	42.2		%
Risk-free interest rate	1.2		%	0.5		%	0.7		%	0.6		%
Expected dividends	0.8		%	1.3		%	0.9		%	1.3		%
Expected life (in years)	4.2			4.3			4.2			4.3
Weighted-average grant date fair value	$	11.64		$	10.84		$	11.83		$	10.43
ESPP
Expected volatility	24.9		%	38.4		%	24.9		%	38.4		%
Risk-free interest rate	0.1		%	0.1		%	0.1		%	0.1		%
Expected dividends	0.9		%	1.1		%	0.9		%	1.1		%
Expected life (in years)	0.5			0.5			0.5			0.5
Weighted-average grant date fair value	$	9.58		$	8.95		$	9.58		$	8.95