Stock-based Compensation (Tables)

9 Months Ended

Oct. 31, 2019

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,
	2019		2018		2019		2018
	(in thousands)
Stock-based compensation:
Cost of revenue	$	335	$	310	$	922	$	942
Research and development		10,601		9,720		31,306		27,847
Selling, general and administrative		6,372		5,582		17,740		16,148
Total stock-based compensation	$	17,308	$	15,612	$	49,968	$	44,937

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,
	2019			2018			2019			2018
Stock Options:
Volatility		52	%		53	%		52	%		54	%
Risk-free interest rate		1.39	%		2.78	%		1.84	%		2.75	%
Expected term (years)	6.09			5.45			6.02				5.40
Dividend yield		0	%		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		46	%		44	%		47	%		45	%
Risk-free interest rate		1.93	%		2.35	%		2.23	%		2.15	%
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, 2019		1,459,064		$	28.31
Granted		57,350			49.79	$	25.06
Exercised		(338,289	)		15.43			$	12,054
Forfeited		(13,306	)		45.65
Expired		(9,751	)		55.95
Outstanding at October 31, 2019		1,155,068			32.71					4.54		$	26,387
Exercisable at October 31, 2019		981,191		$	29.94						3.80	$	25,280

Restricted Stock and Restricted Stock Units Activities

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

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2019		2,395,516		$	48.49
Granted		1,296,053			54.48
Vested		(775,893	)		51.41
Forfeited		(80,496	)		55.50
Unvested at October 31, 2019		2,835,180		$	50.23