Stock-based Compensation (Tables)

9 Months Ended

Oct. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Classification of Stock-based Compensation

The following table presents the classification of stock-based compensation for the periods indicated:

	Three Months Ended October 31,				Nine Months Ended October 31,
	2020		2019		2020		2019
	(in thousands)
Stock-based compensation:
Cost of revenue	$	368	$	335	$	981	$	922
Research and development		11,496		10,601		31,402		31,306
Selling, general and administrative		7,113		6,372		19,024		17,740
Total stock-based compensation	$	18,977	$	17,308	$	51,407	$	49,968

Weighted-Average Assumptions Used to Estimate Fair Value

The following table sets forth the weighted-average assumptions used to estimate the fair value of stock options and employee stock purchase plan awards for the periods indicated:

	Three Months Ended October 31,						Nine Months Ended October 31,
	2020			2019			2020			2019
Stock Options:
Volatility		52	%		52	%		52	%		52	%
Risk-free interest rate		0.40	%		1.39	%		0.52	%		1.84	%
Expected term (years)	5.81			6.09			5.84			6.02
Dividend yield		0	%		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		58	%		46	%		59	%		47	%
Risk-free interest rate		0.12	%		1.93	%		0.21	%		2.23	%
Expected term (years)	0.5			0.5			0.5			0.5
Dividend yield		0	%		0	%		0	%		0	%

Stock Option Activities

The following table summarizes stock option activities for the period indicated:

	Option Outstanding
										Weighted-
								Total Intrinsic		Average
						Weighted-		Value Of		Remaining		Aggregate
				Weighted-		Average		Options		Contractual		Intrinsic
				Average		Grant-date		Exercised		Term		Value
	Shares			Exercise Price		Fair Value		(in thousands)		(in years)		(in thousands)
Outstanding at January 31, 2020		1,124,646		$	32.93
Granted		36,700			53.05	$	25.45
Exercised		(207,876	)		12.31			$	9,224
Forfeited		(11,301	)		46.74
Expired		(21,422	)		75.47
Outstanding at October 31, 2020		920,747			37.23					4.42		$	18,266
Exercisable at October 31, 2020		790,911		$	35.19						3.75	$	17,504

Restricted Stock Units Activities

The following table summarizes the restricted stock units activities for the period indicated:

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2020		2,617,266		$	50.30
Granted		1,445,544			52.61
Vested		(901,392	)		51.17
Forfeited		(74,109	)		54.87
Unvested at October 31, 2020		3,087,309		$	51.02