Cover - shares	9 Months Ended
	Sep. 30, 2020	Oct. 31, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-35095
Entity Registrant Name	UNITED COMMUNITY BANKS, INC.
Entity Central Index Key	0000857855
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Incorporation, State or Country Code	GA
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
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		86,620,219
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 1/1000th interest in a share of Series I Non-Cumulative Preferred Stock
Trading Symbol	UCBIO
Security Exchange Name	NASDAQ