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Stock-based Compensation (Tables)

3 Months Ended

Apr. 30, 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 April 30,
	2019		2018
	(in thousands)
Stock-based compensation:
Cost of revenue	$	267	$	315
Research and development		10,204		8,760
Selling, general and administrative		5,989		5,120
Total stock-based compensation	$	16,460	$	14,195

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 April 30,
	2019			2018
Stock Options:
Volatility		52	%		55	%
Risk-free interest rate		2.49	%		2.65	%
Expected term (years)	5.88			5.33
Dividend yield		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		18,800			42.13	$	21.57
Exercised		(101,645	)		14.95			$	2,767
Forfeited		(6,448	)		46.81
Expired		(5,358	)		66.87
Outstanding at April 30, 2019		1,364,413			29.25					4.46		$	32,360
Exercisable at April 30, 2019		1,170,168		$	26.28						3.76	$	31,285

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		407,076			48.11
Vested		(252,076	)		53.12
Forfeited		(17,322	)		48.20
Unvested at April 30, 2019		2,533,194		$	47.97