Stock-based Compensation (Tables)

3 Months Ended

Apr. 30, 2015

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,
	2015		2014
	(in thousands)
Stock-based compensation:
Cost of revenue	$	124	$	59
Research and development		3,094		1,590
Selling, general and administrative		2,264		1,225
Total stock-based compensation	$	5,482	$	2,874

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,
	2015			2014
Stock Options:
Volatility		60	%		65	%
Risk-free interest rate		1.74	%		1.95	%
Expected term (years)	6.08				6.05
Dividend yield		0	%		0	%
Employee stock purchase plan awards:
Volatility		63	%		57	%
Risk-free interest rate		0.15	%		0.08	%
Expected term (years)		0.5			0.5
Dividend yield		0	%		0	%

Stock Option Activities

The following table summarizes stock option activities for the three months ended April 30, 2015:

	Option Outstanding
										Weighted-
								Total Intrinsic		Average
						Weighted-		Value of		Remaining		Aggregate
				Weighted-		Average		options		Contactual		Intrinsic
				Average		Grant-date		Exercised		Term		Value
	Shares			Exercise Price		Fair Value		(in thousands)		(in years)		(in thousands)
Outstanding at January 31, 2015		2,281,909		$	13.00
Granted		66,100			64.39	$	36.30
Exercised		(272,334	)		7.88			$	16,431
Forfeited		(5,580	)		24.62
Outstanding at April 30, 2015		2,070,095			15.28					6.36		$	119,790
Exercisable at April 30, 2015		1,399,112		$	7.99						5.32	$	91,169
Vested and expected to vest at April 30, 2015		2,027,575		$	14.84						6.31	$	118,221

Restricted Stock Unit Activities

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

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2015		1,980,448		$	26.82
Granted		22,000			64.39
Vested		(178,534	)		23.87
Forfeited		(2,459	)		35.97
Unvested at April 30, 2015		1,821,455		$	27.55