Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2019	Jun. 29, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	UNITED COMMUNITY BANKS INC
Entity Central Index Key	0000857855
Trading Symbol	ucbi
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding		79,256,160
Entity Public Float			$ 2,411,814,691
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY