Commitments and Contingencies - Additional Information (Detail) - USD ($) |
3 Months Ended | 12 Months Ended |
|---|---|---|
Apr. 30, 2019 |
Jan. 31, 2019 |
|
| Loss Contingencies [Line Items] | ||
| Total manufacturing purchase commitments | $ 22,900,000 | $ 28,200,000 |
| Indemnification agreement [Member] | ||
| Loss Contingencies [Line Items] | ||
| Payments under indemnification obligations | 0 | 0 |
| Liabilities recorded under indemnification obligations | $ 0 | $ 0 |