Employee Benefits and Stock-based Compensation (Tables)

12 Months Ended

Jan. 31, 2019

Classification of Stock-based Compensation

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

	Year Ended January 31,
	2019		2018		2017
	(in thousands)
Stock-based compensation:
Cost of revenue	$	1,261	$	1,306	$	1,078
Research and development		37,432		34,575		29,729
Selling, general and administrative		22,119		20,980		18,025
Total stock-based compensation	$	60,812	$	56,861	$	48,832

Weighted-Average Assumptions Used to Estimate Fair Value

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

	Year Ended January 31,
	2019			2018			2017
Stock Options:
Volatility		54	%		53	%		38	%
Risk-free interest rate		2.77	%		2.08	%		1.59	%
Expected term (years)		5.41			6.08			6.00
Dividend yield		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		45	%		44	%		54	%
Risk-free interest rate		2.15	%		1.03	%		0.51	%
Expected term (years)		0.5			0.5			0.5
Dividend yield		0	%		0	%		0	%

Stock Option Activities

The following table summarizes stock option activities for the periods 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, 2016		1,853,390		$	19.36
Granted		110,500			47.82	$	18.76
Exercised		(235,923	)		13.69			$	10,788
Forfeited		(16,708	)		55.07
Expired		(7,735	)		14.19
Outstanding at January 31, 2017		1,703,524			21.66
Granted		132,250			54.66	$	28.28
Exercised		(175,187	)		12.50			$	7,446
Forfeited		(27,721	)		56.97
Expired		(21,522	)		36.31
Outstanding at January 31, 2018		1,611,344		$	24.56
Granted		116,600			42.73	$	21.75
Exercised		(232,205	)		5.54			$	8,867
Forfeited		(20,974	)		53.50
Expired		(15,701	)		54.35
Outstanding at January 31, 2019		1,459,064		$	28.31					4.51		$	22,274
Exercisable at January 31, 2019		1,250,507		$	24.93						3.80	$	22,273

Restricted Stock and Restricted Stock Units Activities

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

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2016		2,495,488		$	47.04
Granted		676,598			67.68
Vested		(955,230	)		39.28
Forfeited		(41,183	)		52.49
Unvested at January 31, 2017		2,175,673			56.76
Granted		1,052,235			47.11
Vested		(1,006,130	)		47.55
Forfeited		(118,497	)		54.72
Unvested at January 31, 2018		2,103,281		$	56.45
Granted		1,367,751			40.03
Vested		(994,500	)		53.27
Forfeited		(81,016	)		53.57
Unvested at January 31, 2019		2,395,516		$	48.49