Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($)
|
3 Months Ended |
12 Months Ended |
Apr. 30, 2018 |
Jan. 31, 2018 |
| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
|
|
| Number of shares, Options outstanding, Beginning Balance |
16,024,146
|
|
| Number of shares, Options granted |
175,000
|
|
| Number of shares, Options exercised |
(788,378)
|
|
| Number of shares, Options forfeited/cancelled |
(153,551)
|
|
| Number of shares, Options outstanding, Ending Balance |
15,257,217
|
16,024,146
|
| Number of shares, Options vested and exercisable |
6,342,353
|
|
| Number of shares, Options vested and exercisable and expected to vest thereafter |
15,257,217
|
|
| Weighted average exercise price, Options outstanding, Beginning Balance |
$ 16.76
|
|
| Weighted average exercise price, Options granted |
77.88
|
|
| Weighted average exercise price, Options exercised |
9.30
|
|
| Weighted average exercise price, Options forfeited/cancelled |
4.00
|
|
| Weighted average exercise price, Options outstanding, Ending Balance |
17.98
|
$ 16.76
|
| Weighted average exercise price, Options vested and exercisable |
5.47
|
|
| Weighted average exercise price, Options vested and exercisable and expected to vest thereafter |
$ 17.98
|
|
| Weighted average remaining contractual term (in years), Options outstanding |
6 years
|
6 years 1 month 6 days
|
| Weighted average remaining contractual term (in years), Options vested and exercisable |
4 years 8 months 12 days
|
|
| Weighted average remaining contractual term (in years), Options vested and exercisable and expected to vest thereafter |
6 years
|
|
| Aggregate intrinsic value, Options outstanding |
$ 797,016,507
|
$ 738,648,507
|
| Aggregate intrinsic value, Options vested and exercisable |
410,121,313
|
|
| Aggregate intrinsic value, Options vested and exercisable and expected to vest thereafter |
$ 797,016,507
|
|