| Cover | Mar. 22, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 22, 2021 |
| Entity File Number | 001-40136 |
| Entity Registrant Name | AMALGAMATED FINANCIAL CORP. |
| Entity Central Index Key | 0001823608 |
| Entity Tax Identification Number | 85-2757101 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 275 Seventh Avenue |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10001 |
| City Area Code | (212) |
| Local Phone Number | 895-8988 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.01 per share |
| Trading Symbol | AMAL |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| Entity Information, Former Legal or Registered Name | Not Applicable |
