| Postemployment Benefits [Abstract] | Period [Axis] |
|---|
2016-02-01 - 2017-01-31 |
|---|
Postemployment Benefits [Abstract] | |
Classification of Stock-based Compensation |
The following table presents the classification of stock-based compensation for the periods indicated:
|
|
|
Year Ended January 31, |
|
|
|
|
2017 |
|
|
2016 |
|
|
2015 |
|
|
|
|
(in thousands) |
|
|
Stock-based compensation: |
|
|
|
|
|
|
|
|
|
|
|
|
|
Cost of revenue |
|
$ |
1,078 |
|
|
$ |
657 |
|
|
$ |
343 |
|
|
Research and development |
|
|
29,729 |
|
|
|
19,082 |
|
|
|
8,654 |
|
|
Selling, general and administrative |
|
|
18,025 |
|
|
|
11,355 |
|
|
|
6,695 |
|
|
Total stock-based compensation |
|
$ |
48,832 |
|
|
$ |
31,094 |
|
|
$ |
15,692 |
|
|
Weighted-Average Assumptions Used to Estimate Fair Value |
The following table sets forth the weighted-average assumptions used to estimate the fair value of the stock options and employee stock purchase plan awards for the periods indicated:
|
|
|
Year Ended January 31, |
|
|
|
|
2017 |
|
|
2016 |
|
|
2015 |
|
|
Stock Options: |
|
|
|
|
|
|
|
|
|
|
|
|
|
Volatility |
|
|
38 |
% |
|
|
57 |
% |
|
|
64 |
% |
|
Risk-free interest rate |
|
|
1.59 |
% |
|
|
1.74 |
% |
|
|
1.93 |
% |
|
Expected term (years) |
|
|
6.00 |
|
|
6.08 |
|
|
6.01 |
|
|
Dividend yield |
|
|
0 |
% |
|
|
0 |
% |
|
|
0 |
% |
|
Employee stock purchase plan awards: |
|
|
|
|
|
|
|
|
|
|
|
|
|
Volatility |
|
|
54 |
% |
|
|
63 |
% |
|
|
49 |
% |
|
Risk-free interest rate |
|
|
0.51 |
% |
|
|
0.21 |
% |
|
|
0.07 |
% |
|
Expected term (years) |
|
|
0.5 |
|
|
|
0.5 |
|
|
|
0.5 |
|
|
Dividend yield |
|
|
0 |
% |
|
|
0 |
% |
|
|
0 |
% |
|
Stock Option Activities |
The following table summarizes stock option activities for the periods indicated:
|
|
|
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, 2014 |
|
|
3,358,706 |
|
|
$ |
6.92 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Granted |
|
|
428,781 |
|
|
|
36.33 |
|
|
$ |
21.37 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Exercised |
|
|
(1,456,944 |
) |
|
|
5.84 |
|
|
|
|
|
|
$ |
46,427 |
|
|
|
|
|
|
|
|
|
|
Forfeited |
|
|
(48,634 |
) |
|
|
13.38 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Outstanding at January 31, 2015 |
|
|
2,281,909 |
|
|
|
13.00 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Granted |
|
|
179,700 |
|
|
|
71.36 |
|
|
$ |
38.81 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Exercised |
|
|
(567,888 |
) |
|
|
9.11 |
|
|
|
|
|
|
$ |
37,603 |
|
|
|
|
|
|
|
|
|
|
Forfeited |
|
|
(40,331 |
) |
|
|
35.65 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Outstanding at January 31, 2016 |
|
|
1,853,390 |
|
|
|
19.36 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Granted |
|
|
110,500 |
|
|
|
47.82 |
|
|
$ |
18.76 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Exercised |
|
|
(235,923 |
) |
|
|
13.69 |
|
|
|
|
|
|
$ |
10,788 |
|
|
|
|
|
|
|
|
|
|
Forfeited |
|
|
(16,708 |
) |
|
|
55.07 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Expired |
|
|
(7,735 |
) |
|
|
14.19 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Outstanding at January 31, 2017 |
|
|
1,703,524 |
|
|
$ |
21.66 |
|
|
|
|
|
|
|
|
|
|
5.16 |
|
|
$ |
51,670 |
|
|
Exercisable at January 31, 2017 |
|
|
1,367,960 |
|
|
$ |
14.94 |
|
|
|
|
|
|
|
|
|
|
|
4.42 |
|
|
$ |
49,016 |
|
|
Restricted Stock and Restricted Stock Units Activities |
The following table summarizes restricted stock and restricted stock units activities for the periods indicated:
|
|
|
|
|
|
|
Weighted- |
|
|
|
|
|
|
|
|
Average |
|
|
|
|
|
|
|
|
Grant-Date |
|
|
|
|
Shares |
|
|
Fair Value |
|
|
Unvested at January 31, 2014 |
|
|
1,410,089 |
|
|
$ |
14.02 |
|
|
Granted |
|
|
1,111,204 |
|
|
|
38.60 |
|
|
Vested |
|
|
(484,296 |
) |
|
|
17.39 |
|
|
Forfeited |
|
|
(56,549 |
) |
|
|
19.93 |
|
|
Unvested at January 31, 2015 |
|
|
1,980,448 |
|
|
|
26.82 |
|
|
Granted |
|
|
1,314,387 |
|
|
|
66.14 |
|
|
Vested |
|
|
(769,779 |
) |
|
|
27.82 |
|
|
Forfeited |
|
|
(29,568 |
) |
|
|
42.11 |
|
|
Unvested at January 31, 2016 |
|
|
2,495,488 |
|
|
|
47.04 |
|
|
Granted |
|
|
676,598 |
|
|
|
67.68 |
|
|
Vested |
|
|
(955,230 |
) |
|
|
39.28 |
|
|
Forfeited |
|
|
(41,183 |
) |
|
|
52.49 |
|
|
Unvested at January 31, 2017 |
|
|
2,175,673 |
|
|
$ |
56.76 |
|
|