Derivatives and Hedging Activities - Carrying Amount and Cumulative Fair Value Hedging Adjustments on Hedged Liability (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Hedge Accounting Basis Adjustment	$ (402)	$ 1,893
Fair Value Hedging \| Debt Securities AFS
Derivative [Line Items]
Carrying Amount	783,148	789,908
Hedge Accounting Basis Adjustment	(14,471)	(4,673)
Fair Value Hedging \| Loans and leases held for investment
Derivative [Line Items]
Carrying Amount	5,408,116	1,017,379
Hedge Accounting Basis Adjustment	(402)	1,893
Fair Value Hedging \| Debt Securities AFS
Derivative [Line Items]
Hedged Portfolio Layer	649,520	655,511
Fair Value Hedging \| Loans and leases held for investment
Derivative [Line Items]
Hedged Portfolio Layer	$ 1,650,000	$ 150,000

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-5

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of asset hedged in portfolio layer hedging relationship, expected to be remaining at end of hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EEE
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4EEE

+ Details

Name:	us-gaap_HedgedAssetFairValueHedgeLastOfLayerAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, in portfolio layer hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480401/815-10-55-181

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EEE
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4EEE

+ Details

Name:	us-gaap_HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, in portfolio layer hedging relationship, excluded from amortized cost of asset included in closed portfolio.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-5B

+ Details

Name:	us-gaap_HedgedAssetFairValueHedgePortfolioLayerMethodCumulativeIncreaseDecreaseExcludedFromAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of closed portfolio of financial asset used to designate hedging relationship in which hedged item is expected to be outstanding for designated hedged period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480401/815-10-55-181

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EEE
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4EEE

+ Details

Name:	us-gaap_PrepayableFinancialAssetClosedPortfolioLastOfLayerAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_FairValueHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=ucbi_LoansAndLeasesHeldForInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=ucbi_LoansAndLeasesHeldForInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: