Stockholders' Equity (Tables)
 3 Months Ended
Apr. 30, 2019
Equity [Abstract]  
Stock option activity
Option activity for the three months ended April 30, 2019, was as follows:
(in thousands, except per share and years data)
Number of Options Outstanding
 
Weighted-Average Exercise Price Per Share
 
Weighted-Average Remaining Contractual Term (Years)
 
Aggregate Intrinsic Value
Outstanding at January 31, 2019
13,648

 
$
12.27

 
5.38
 
$
507,371

Options exercised
(2,634
)
 
10.82

 
 
 
 
Options canceled/expired
(25
)
 
17.69

 
 
 
 
Outstanding at April 30, 2019
10,989

 
$
12.61

 
5.41
 
$
484,184

Vested and expected to vest at April 30, 2019
10,852

 
$
12.55

 
5.38
 
$
478,824

Exercisable at April 30, 2019
9,418

 
$
11.77

 
5.05
 
$
422,811
RSU activity
RSU activity for the three months ended April 30, 2019, was as follows:
(in thousands, except per share data)
Number of Units
 
Weighted-Average Grant Date Fair Value
Unvested at January 31, 2019
17,142

 
$
34.56

Granted
1,174

 
55.42

Vested
(2,468
)
 
20.72

Canceled
(821
)
 
37.23

Unvested at April 30, 2019
15,027

 
$
38.32