Stock-based Compensation (Tables)

6 Months Ended

Jul. 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 July 31,				Six Months Ended July 31,
	2020		2019		2020		2019
	(in thousands)
Stock-based compensation:
Cost of revenue	$	316	$	320	$	613	$	587
Research and development		10,010		10,501		19,906		20,705
Selling, general and administrative		6,068		5,379		11,911		11,368
Total stock-based compensation	$	16,394	$	16,200	$	32,430	$	32,660

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 July 31,						Six Months Ended July 31,
	2020			2019			2020			2019
Stock Options:
Volatility		53	%		52	%		52	%		52	%
Risk-free interest rate		0.52	%		1.95	%		0.59	%		2.31	%
Expected term (years)	5.84			6.09			5.86			5.95
Dividend yield		0	%		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		—			—			61	%		48	%
Risk-free interest rate		—			—			0.29	%		2.52	%
Expected term (years)		—			—		0.5			0.5
Dividend yield		—			—			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		23,600			53.54	$	25.73
Exercised		(99,911	)		14.57			$	4,293
Forfeited		(7,115	)		48.88
Expired		(13,853	)		82.55
Outstanding at July 31, 2020		1,027,367			34.41					4.17		$	15,936
Exercisable at July 31, 2020		885,276		$	31.99						3.48	$	15,670

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		536,894			53.35
Vested		(647,471	)		51.33
Forfeited		(59,726	)		56.14
Unvested at July 31, 2020		2,446,963		$	50.56