Stock-based Compensation

6 Months Ended

Jul. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

10. 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

During the three and six months ended July 31, 2019, approximately $1.2 million and $2.2 million of stock-based compensation expense was accrued in the accrued and other current liabilities in the condensed consolidated balance sheets, respectively. As of July 31, 2019, total unrecognized compensation cost related to unvested stock options was $3.8 million and is expected to be recognized over a weighted-average period of 2.55 years. Total unrecognized compensation cost related to unvested restricted stock units was $96.2 million and is expected to be recognized over a weighted-average period of 2.42 years. Total unrecognized compensation cost related to unvested restricted stock awards was $0.1 million and is expected to be recognized over a weighted-average period of 0.13 years.

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	%

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

The intrinsic value of options outstanding and exercisable is calculated based on the difference between the fair market value of the Company’s ordinary shares on the reporting date and the exercise price. The closing price of the Company’s ordinary shares on July 31, 2019 was $49.95, as reported by The NASDAQ Global Market. The intrinsic value of exercised options is calculated by the difference between the fair market value of the Company’s ordinary shares on the exercise date and the exercise price.

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

As of July 31, 2019, the aggregate intrinsic value of unvested restricted stock and restricted stock units was $114.8 million.