Stock-Based Compensation (Tables)

12 Months Ended

Jan. 31, 2019

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:

	SharesSubject 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		1,533,056			17.46
Option exercised		(2,098,726	)		6.94
Options forfeited/cancelled		(910,010	)		15.03
Balance as of January 31, 2018		10,843,120		$	8.32		5.74	$	150,922
Options granted		717,658			20.78
Option exercised		(1,980,070	)		8.24
Options forfeited/cancelled		(483,747	)		14.23
Balance as of January 31, 2019		9,096,961		$	9.01		4.97	$	108,731
Vested and expected to vest as of January 31, 2019		9,033,624		$	8.94		4.94	$	108,591
Exercisable as of January 31, 2019		7,706,805		$	7.21		4.31	$	105,673

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		7,807,240			18.11
Vested, net of shares withheld for employee payroll taxes		(3,007,876	)		14.68
Forfeited/cancelled		(2,002,428	)		15.24
Unvested balance - January 31, 2018		14,619,252		$	16.42
Granted		10,349,570			22.12
Vested, net of shares withheld for employee payroll taxes		(3,344,632	)		16.84
Forfeited/cancelled		(3,525,483	)		17.72
Unvested balance - January 31, 2019		18,098,707		$	19.35

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):

	Year Ended January 31,
	2019		2018		2017
Cost of revenue	$	14,065	$	10,742	$	7,882
Research and development		45,189		37,733		30,796
Sales and marketing		36,864		31,742		26,142
General and administrative		23,178		17,268		13,552
Total stock-based compensation	$	119,296	$	97,485	$	78,372

Summary of Estimated Fair Value of Employee Stock Options

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

	Year Ended January 31,
	2019					2018					2017
Employee Stock Options
Expected term (in years)		5.5	–		5.8		5.5	–		6.1		5.5	–		6.0
Risk-free interest rate	2.8%		–	3.1%		1.8%		–	2.1%		1.3%		–	2.0%
Volatility				45%		38%		–	40%		40%		–	43%
Dividend yield				0%					0%					0%
Employee Stock Purchase Plan
Expected term (in years)		0.5	–		2.0		0.5	–		2.0	0.5		–		2.0
Risk-free interest rate	2.0%		–	2.8%		0.9%		–	1.4%		0.5%		–	0.9%
Volatility	37%		–	50%		28%		–	43%		39%		–	60%
Dividend yield				0%					0%					0%