Stock-based Compensation

3 Months Ended

Apr. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

10. 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

During the three months ended April 30, 2019, approximately $1.0 million of stock-based compensation was accrued in the accrued and other current liabilities in the condensed consolidated balance sheets. As of April 30, 2019, total unrecognized compensation cost related to unvested stock options was $4.3 million and is expected to be recognized over a weighted-average period of 2.62 years. Total unrecognized compensation cost related to unvested restricted stock units was $110.3 million and is expected to be recognized over a weighted-average period of 2.57 years. Total unrecognized compensation cost related to unvested restricted stock awards was $0.6 million and is expected to be recognized over a weighted-average period of 0.29 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 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	%

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

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 April 30, 2019 was $50.12, 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		407,076			48.11
Vested		(252,076	)		53.12
Forfeited		(17,322	)		48.20
Unvested at April 30, 2019		2,533,194		$	47.97

As of April 30, 2019, the aggregate intrinsic value of unvested restricted stock and restricted stock units was $127.0 million.