Stock Award Plans and Stock-Based Compensation (Tables)

12 Months Ended

Mar. 31, 2019

Stock-Based Compensation Recognized

The following table summarizes stock-based compensation expense by financial statement line item in the Company’s consolidated statements of operations for the fiscal years ended March 31, 2019, 2018 and 2017:

	Fiscal Years Ended March 31,
		2019		2018		2017
	(in $000's)
Cost of revenue	$	2,643	$	1,721	$	1,061
Research and development		9,312		5,895		6,050
Selling, general and administrative		42,539		32,737		25,755
	$	54,494	$	40,353	$	32,866

Components of Stock-Based Compensation

The components of stock-based compensation for the fiscal years ended March 31, 2019, 2018 and 2017 were as follows:

	Fiscal Years Ended March 31,
		2019		2018		2017
	(in $000's)
Restricted stock units	$	45,998	$	34,559	$	26,570
Stock options		7,445		5,202		5,829
Employee stock purchase plan		1,051		592		467
	$	54,494	$	40,353	$	32,866

Summary of Stock Option Activity

The following table summarized stock option activity for the fiscal year ended March 31, 2019:

						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Options			Exercise		Contractual		Value
	(in thousands)			Price		Term (years)		(in thousands)
Outstanding at beginning of period		1,282		$	46.81		5.31	$	313,158
Granted		81			379.90
Exercised		(485	)		26.68
Cancelled and expired		(25	)		138.68
Outstanding at end of period		853		$	87.14		5.57	$	176,629
Exercisable at end of period		623		$	40.72		4.58	$	152,598

Summary of Weighted Average Grant-Date Fair Values And Weighted Average Assumptions Used to Calculate Fair Value of Options Granted

The weighted average grant-date fair values and weighted average assumptions used in the calculation of fair value of options granted during the fiscal years ended March 31, 2019, 2018 and 2017 was as follows:

	Fiscal Years Ended March 31,
		2019			2018			2017
Valuation assumptions:
Weighted average grant-date fair value	$	141.47		$	52.34		$	42.40
Risk-free interest rate		2.91	%		1.87	%		1.41	%
Expected option life (years)		4.04			4.07			4.14
Expected volatility		42.8	%		43.5	%		48.9	%

Restricted Stock Units

Summary of Restricted Stock Units Activity

The following table summarizes restricted stock unit activity for the fiscal year ended March 31, 2019:

	Number of Shares			Weighted Average Grant Date Fair Value
	(in thousands)			(per share)
Restricted stock units at beginning of period		880		$	109.01
Granted		195			376.95
Vested		(427	)		103.54
Forfeited		(28	)		189.05
Restricted stock units at end of period		620		$	193.53

Monte Carlo Simulation Model to Estimate Grant-Date Fair Value of Restricted Stock Units

The table below sets forth the assumptions used to value the market-based awards and the estimated grant-date fair value:

	June 2015 Awards			November 2016 Awards
Risk-free interest rate		1.10	%		0.90	%
Dividend yield		0	%		0	%
Remaining performance period (years)		0.21			0.21
Expected volatility		47.2	%		50.6	%
Estimated grant date fair value (per share)	$   93.49 - 107.10			$	62.55
Target performance (number of shares)		107,660			41,526