| Document and Entity Information | Oct. 26, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | AMBARELLA INC |
| Entity Incorporation State Country Code | RI |
| Amendment Flag | false |
| Entity Central Index Key | 0001280263 |
| Document Type | 8-K |
| Document Period End Date | Oct. 26, 2021 |
| Entity File Number | 001-35667 |
| Entity Tax Identification Number | 98-0459628 |
| Entity Address, Address Line One | 3101 Jay Street |
| Entity Address, City or Town | Santa Clara |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95054 |
| City Area Code | (408) |
| Local Phone Number | 734-8888 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Ordinary Shares, $0.00045 par value |
| Trading Symbol | AMBA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
