Stock-based Compensation (Tables)

6 Months Ended

Jul. 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 July 31,				Six Months Ended July 31,
	2019		2018		2019		2018
	(in thousands)
Stock-based compensation:
Cost of revenue	$	320	$	317	$	587	$	632
Research and development		10,501		9,367		20,705		18,127
Selling, general and administrative		5,379		5,446		11,368		10,566
Total stock-based compensation	$	16,200	$	15,130	$	32,660	$	29,325

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,
	2019			2018			2019			2018
Stock Options:
Volatility		52	%		55	%		52	%		55	%
Risk-free interest rate		1.95	%		2.77	%		2.31	%		2.73	%
Expected term (years)	6.09			5.38			5.95			5.36
Dividend yield		0	%		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		—			—			48	%		46	%
Risk-free interest rate		—			—			2.52	%		1.95	%
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, 2019		1,459,064		$	28.31
Granted		28,300			41.07	$	21.00
Exercised		(163,886	)		15.30			$	4,493
Forfeited		(11,508	)		45.29
Expired		(9,045	)		56.55
Outstanding at July 31, 2019		1,302,925			29.87					4.31		$	30,053
Exercisable at July 31, 2019		1,130,044		$	27.35						3.64	$	29,049

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		455,822			47.47
Vested		(506,269	)		52.59
Forfeited		(47,522	)		51.49
Unvested at July 31, 2019		2,297,547		$	47.32