Stock-Based Compensation (Tables)

6 Months Ended

Jul. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity Under Equity Incentive Plans and Related Information

The following table summarizes the stock option activity under the equity incentive plans and related information:

	Shares Subject to Options Outstanding					Weighted-Average
				Weighted-		Remaining
				Average Exercise		Contractual Life		Aggregate
	Shares			Price		(Years)		Intrinsic Value
								(in thousands)
Balance as of January 31, 2017		12,318,800		$	7.44		6.42	$	119,606
Options granted		1,133,056			16.91
Option exercised		(930,595	)		5.82
Options forfeited/cancelled		(784,749	)		15.26
Balance as of July 31, 2017		11,736,512		$	7.96		6.12	$	127,825
Vested and expected to vest as of July 31, 2017		11,628,379		$	7.90		6.10	$	127,359
Exercisable as of July 31, 2017		9,164,951		$	6.11		5.49	$	116,739

Summary of Restricted Stock Unit Activity Under Equity Incentive Plans and Related Information

The following table summarizes the restricted stock unit activity under the equity incentive plans and related information:

	Number of			Weighted-
	Restricted			Average
	Stock Units			Grant Date
	Outstanding			Fair Value
Unvested balance - January 31, 2017		11,822,316		$	14.67
Granted		5,260,434			17.57
Vested, net of shares withheld for employee payroll taxes		(1,297,031	)		13.68
Forfeited/cancelled, including shares withheld for employee payroll taxes		(1,603,930	)		14.38
Unvested balance - July 31, 2017		14,181,789		$	15.87

Summary of Components of Stock-Based Compensation Expense

The following table summarizes the components of stock-based compensation expense recognized in the consolidated statements of operations (in thousands):

	Three Months Ended				Six Months Ended
	July 31,				July 31,
	2017		2016		2017		2016
Cost of revenue	$	2,663	$	1,830	$	5,131	$	3,342
Research and development		9,554		7,348		18,714		13,872
Sales and marketing		7,934		6,416		15,674		11,646
General and administrative		3,916		3,470		7,494		6,293
Total stock-based compensation	$	24,067	$	19,064	$	47,013	$	35,153

Summary of Estimated Fair Value of Employee Stock Options

We estimated the fair value of employee stock options and 2015 ESPP purchase rights using generally a Black-Scholes option pricing model with the following assumptions:

	Three Months Ended										Six Months Ended
	July 31,										July 31,
	2017					2016					2017					2016
Employee Stock Options
Expected term (in years)		5.5		-	6.0		5.5		-	6.0		5.5		-	6.0		5.5		-	6.0
Risk-free interest rate		1.8	%	-	2.0%		1.3	%	-	1.5%		1.8	%	-	2.4%		1.3	%	-	1.5%
Volatility		38	%	-	39%					43%		38	%	-	40%					43%
Dividend yield					0%					0%					0%					0%
Employee Stock Purchase Plan
Expected term (in years)		0.5		-	2.0	0.5			-	2.0		0.5		-	2.0	0.5			-	2.0
Risk-free interest rate		0.9	%	-	1.4%		0.5	%	-	0.9%		0.9	%	-	1.4%		0.5	%	-	0.9%
Volatility		28	%	-	43%		46	%	-	60%		28	%	-	43%		46	%	-	60%
Dividend yield					0%					0%					0%					0%