| Document And Entity Information | Jan. 26, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | Box, Inc. |
| Amendment Flag | false |
| Entity Central Index Key | 0001372612 |
| Document Type | 8-K |
| Document Period End Date | Feb. 26, 2020 |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36805 |
| Entity Tax Identification Number | 20-2714444 |
| Entity Address, Address Line One | 900 Jefferson Ave |
| Entity Address, City or Town | Redwood City |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94063 |
| City Area Code | 877 |
| Local Phone Number | 729-4269 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Security 12b Title | Class A Common Stock, $0.0001 parvalue per share |
| Trading Symbol | BOX |
| Security Exchange Name | NYSE |
