| Document And Entity Information | Nov. 10, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 10, 2021 |
| Entity Registrant Name | Aeva Technologies, Inc. |
| Entity Central Index Key | 0001789029 |
| Entity Emerging Growth Company | true |
| Entity File Number | 001-39204 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 84-3080757 |
| Entity Address, Address Line One | 555 Ellis Street |
| Entity Address, City or Town | Mountain View |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94043 |
| City Area Code | (650) |
| Local Phone Number | 481-7070 |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Ex Transition Period | false |
| Warrants to Purchase [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants to purchase one share of common stock |
| Trading Symbol | AEVA.WS |
| Security Exchange Name | NYSE |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common stock, par value $0.0001 per share |
| Trading Symbol | AEVA |
| Security Exchange Name | NYSE |
