Stock-based Compensation (Tables)

9 Months Ended

Oct. 31, 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 October 31,				Nine Months Ended October 31,
	2015		2014		2015		2014
	(in thousands)
Stock-based compensation:
Cost of revenue	$	157	$	97	$	408	$	214
Research and development		5,201		2,363		11,966		5,582
Selling, general and administrative		2,587		1,824		7,174		4,311
Total stock-based compensation	$	7,945	$	4,284	$	19,548	$	10,107

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 October 31,						Nine Months Ended October 31,
	2015			2014			2015			2014
Stock Options:
Volatility		55	%		63	%		57	%		64	%
Risk-free interest rate		1.70	%		1.94	%		1.73	%		1.94	%
Expected term (years)	6.08				5.97		6.08				6.00
Dividend yield		0	%		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		63	%		40	%		63	%		40	%
Risk-free interest rate		0.27	%		0.05	%		0.21	%		0.05	%
Expected term (years)		0.5			0.5			0.5			0.5
Dividend yield		0	%		0	%		0	%		0	%

Stock Option Activities

The following table summarizes stock option activities for the nine months ended October 31, 2015:

	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, 2015		2,281,909		$	13.00
Granted		163,200			73.06	$	39.79
Exercised		(509,933	)		9.28			$	35,157
Forfeited		(31,081	)		28.91
Outstanding at October 31, 2015		1,904,095			18.89					6.08		$	62,057
Exercisable at October 31, 2015		1,363,586		$	9.41						5.04	$	54,587
Vested and expected to vest at October 31, 2015		1,868,541		$	18.32						6.03	$	61,700

Restricted Stock Activities

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

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2015		1,980,448		$	26.82
Granted		1,264,079			66.57
Vested		(538,487	)		25.20
Forfeited		(24,439	)		38.44
Unvested at October 31, 2015		2,681,601		$	45.78