Financial Instruments and Fair Value - Schedule of Cash Equivalents and Marketable Debt Securities (Detail) - USD ($) $ in Thousands |
Apr. 30, 2019 |
Jan. 31, 2019 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Total cash equivalents and marketable debt securities | $ 206,752 | $ 205,106 |
| Included in cash equivalents [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Total cash equivalents and marketable debt securities | 45,020 | 40,245 |
| Included in marketable debt securities [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Total cash equivalents and marketable debt securities | $ 161,732 | $ 164,861 |