| Document and Entity Information | Oct. 20, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001634997 |
| Document Type | 8-K |
| Document Period End Date | Oct. 20, 2021 |
| Entity Registrant Name | Avangrid, Inc. |
| Entity Incorporation State Country Code | NY |
| Entity File Number | 001-37660 |
| Entity Tax Identification Number | 14-1798693 |
| Entity Address, Address Line One | 180 Marsh Hill Road |
| Entity Address, City or Town | Orange |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06477 |
| City Area Code | (207) |
| Local Phone Number | 629-1200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock |
| Trading Symbol | AGR |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
