STOCK PLANS AND STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Mar. 31, 2019

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

Stock-Based Compensation Expense Included in Statements of Operations

The following table summarizes the amount of stock-based compensation expense included in the consolidated statements of operations for the periods presented:

	Fiscal Year Ended March 31,
(in thousands)	2017			2018			2019
Cost of revenues	$	3,244		$	3,622		$	4,176
Research, development and engineering	8,616			8,071			11,699
Selling, general and administrative	21,679			22,266			26,059
Stock-based compensation expense included in operating expenses	30,295			30,337			37,758
Total stock-based compensation	33,539			33,959			41,934
Income tax benefit	(10,768		)	(7,880		)	(9,891		)
Total stock-based compensation expense, net of tax	$	22,771		$	26,079		$	32,043

Summary of Stock Option Activity

The following is a summary of the Company’s stock option activity during Fiscal Year 2019:

	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, 2018	923		$	47.53
Options granted	—		$	—
Options exercised	(277	)	$	45.07
Options forfeited or expired	(18	)	$	46.06
Outstanding at March 31, 2019	627		$	48.66	2.4	$	670
Vested or expected to vest at March 31, 2019	627		$	48.66	2.4	$	670
Exercisable at March 31, 2019	594		$	48.80	2.2	$	640

Summary of Restricted Stock Activity

The following table summarizes the changes in unvested restricted stock, RSUs, and PSUs, for Fiscal Year 2019:

	Number of Shares		Weighted Average Grant Date Fair Value
	(in thousands)
Unvested at March 31, 2018	1,254		$	51.09
Granted	1,171		$	68.68
Vested	(572	)	$	50.24
Forfeited	(235	)	$	60.44
Non-vested at March 31, 2019	1,618		$	62.77

Valuation Assumptions

The Company estimates the fair value of stock options and ESPP shares using a Black-Scholes option valuation model.  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:

	Employee Stock Options							ESPP
Fiscal Year Ended March 31,	2017			2018			2019	2017			2018			2019
Expected volatility	31.1		%	29.1		%	n/a	28.8		%	30.5		%	40.8		%
Risk-free interest rate	1.1		%	1.7		%	n/a	0.6		%	1.5		%	2.4		%
Expected dividends	1.4		%	1.2		%	n/a	1.1		%	1.2		%	1.1		%
Expected life (in years)	4.4			4.6			n/a	0.5			0.5			0.5
Weighted-average grant date fair value	$	10.39		$	12.58		n/a	$	12.03		$	11.78		$	14.44