Stockholders' Equity (Tables)
 3 Months Ended
Apr. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]  
Summary of Stock Option Activity

A summary of stock option activity for the three months ended April 30, 2018 is as follows:

 

 

 

 

 

 

 

 

 

 

 

Weighted

 

 

 

 

 

 

 

 

 

 

 

Weighted

 

 

average

 

 

 

 

 

 

 

 

 

 

 

average

 

 

remaining

 

 

Aggregate

 

 

 

Number

 

 

exercise

 

 

contractual

 

 

intrinsic

 

 

 

of shares

 

 

price

 

 

term (in years)

 

 

value

 

Options outstanding at January 31, 2018

 

 

16,024,146

 

 

$

16.76

 

 

 

6.1

 

 

$

738,648,507

 

Options granted

 

 

175,000

 

 

 

77.88

 

 

 

 

 

 

 

 

 

Options exercised

 

 

(788,378

)

 

 

9.30

 

 

 

 

 

 

 

 

 

Options forfeited/cancelled

 

 

(153,551

)

 

 

4.00

 

 

 

 

 

 

 

 

 

Options outstanding at April 30, 2018

 

 

15,257,217

 

 

$

17.98

 

 

 

6.0

 

 

$

797,016,507

 

Options vested and exercisable at April 30, 2018

 

 

6,342,353

 

 

$

5.47

 

 

 

4.7

 

 

$

410,121,313

 

Options vested and exercisable at April 30, 2018 and

   expected to vest thereafter

 

 

15,257,217

 

 

$

17.98

 

 

 

6.0

 

 

$

797,016,507

 

 

 

 
Summary of Restricted Stock Unit (RSU) Activity

A summary of restricted stock unit (RSU) activity for the three months ended April 30, 2018 is as follows:

 

 

 

Unreleased restricted

 

 

Weighted average grant

 

 

 

stock units

 

 

date fair value

 

Balance at January 31, 2018

 

 

2,901,736

 

 

$

38.14

 

RSUs granted

 

 

637,710

 

 

 

69.94

 

RSUs vested

 

 

(319,124

)

 

 

34.58

 

RSUs forfeited/cancelled

 

 

(62,247

)

 

 

39.70

 

Balance at April 30, 2018

 

 

3,158,075

 

 

$

44.89

 

 

 

 
Schedule of Weighted-Average Assumptions Used to Estimate Grant Date Fair Value of Options Granted

The following table presents the weighted-average assumptions used to estimate the grant date fair value of options granted during the periods presented:

 

 

 

Three months ended

April 30,

 

 

 

2018

 

 

2017

 

Volatility

 

41%

 

 

44%

 

Expected term (in years)

 

 

6.35

 

 

 

6.35

 

Risk-free interest rate

 

2.73%

 

 

1.95% - 2.17%

 

Dividend yield

 

0%

 

 

0%