| Cover Page | Aug. 12, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 12, 2021 |
| Entity Registrant Name | UNITED COMMUNITY BANKS, INC. |
| Entity Central Index Key | 0000857855 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | GA |
| Entity File Number | 001-35095 |
| Entity Tax Identification Number | 58-1807304 |
| Entity Address, Address Line One | 125 Highway 515 East |
| Entity Address, City or Town | Blairsville |
| Entity Address, State or Province | GA |
| Entity Address, Postal Zip Code | 30512 |
| City Area Code | 706 |
| Local Phone Number | 781-2265 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common stock, par value $1 per share | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Common stock, par value $1 per share |
| Trading Symbol | UCBI |
| Security Exchange Name | NASDAQ |
| Depositary shares, each representing 1/1000th interest in a share of Series I Non-Cumulative Preferred Stock | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Depositary shares, each representing 1/1,000th interest in a share of Series I Non-Cumulative Preferred Stock |
| Trading Symbol | UCBIO |
| Security Exchange Name | NASDAQ |
