Stock-Based Compensation (Tables)

6 Months Ended

Sep. 30, 2021

Stock-Based Compensation Recognized

The following table summarizes stock-based compensation expense by financial statement line item in the Company’s condensed consolidated statements of operation for each of the three and six months ended September 30, 2021 and 2020:

	For the Three Months Ended September 30,				For the Six Months Ended September 30,
		2021		2020		2021		2020
	(in thousands)
Cost of revenue	$	1,300	$	923	$	2,330	$	1,627
Research and development		2,294		1,705		4,403		3,147
Selling, general and administrative		12,155		8,937		21,624		16,089
	$	15,749	$	11,565	$	28,357	$	20,863

Summary of Stock Option Activity

The following table summarizes the stock option activity for the six months ended September 30, 2021:

						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Options			Exercise		Contractual		Value
	(in thousands)			Price		Term (years)		(in thousands)
Outstanding at beginning of period		711		$	141.87	5.46
Granted		62			286.76
Exercised		(152	)		55.26
Cancelled and expired		(9	)		283.42
Outstanding at end of period		612		$	175.86		5.90		95,180
Exercisable at end of period		466		$	149.39	4.98			85,599
Options vested and expected to vest at end of period		612		$	175.86		5.90		95,180

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 was as follows: 

	For the Three Months Ended September 30,						For the Six Months Ended September 30,
		2021			2020			2021			2020
Weighted average grant-date fair value	$	115.99		$	100.51		$	103.48		$	76.10
Valuation assumptions:
Risk-free interest rate		0.77	%		0.30	%		0.79	%		0.31	%
Expected option life (years)		4.14			4.17			4.20			4.22
Expected volatility		44.72	%		43.50	%		44.30	%		42.82	%

Restricted Stock Units

Summary of Restricted Stock Units Activity

The following table summarizes activity of restricted stock units for the six months ended September 30, 2021:

				Weighted
				Average
	Number of			Grant Date
	Shares			Fair Value
	(in thousands)			(per share)
Restricted stock units at beginning of period		301		$	273.57
Granted		156			288.64
Vested		(103	)		304.20
Forfeited		(19	)		270.35
Restricted stock units at end of period		335		$	271.32

Summary of Assumptions Used To Value Awards And Estimated Grant-Date Fair Value

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

	May 2021			May  2020
Risk-free interest rate		0.3	%		0.2	%
Expected volatility		44.8	%		35.5	%
Dividend yield		—			—
Remaining performance period (years)		2.8		1.9 - 2.9
Estimated fair value per share	$	292.40		$347.05 - $349.28
Target performance (number of shares)		25,172			30,881