Credit Quality - Schedule of Amortized Cost Basis of Loan Modifications Made to Borrowers (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	$ 0	$ 0	$ 0	$ 5,341
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 3,466
% of Total Class of Financing Receivable	0.02%	0.00%	0.03%	0.12%
Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 2,487	$ 78	$ 3,693	$ 15,643
Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	3,709	0	3,915	4,616
Commercial Real Estate [Member] \| Owner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	0	0	0	0
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 3,466
% of Total Class of Financing Receivable	0.00%	0.00%	0.06%	0.56%
Commercial Real Estate [Member] \| Owner-Occupied [Member] \| Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 0	$ 0	$ 1,206	$ 8,402
Commercial Real Estate [Member] \| Owner-Occupied [Member] \| Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	0	0	37	0
Commercial Real Estate [Member] \| Nonowner-Occupied [Member]
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	0	0	0	5,341
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 0
% of Total Class of Financing Receivable	0.00%	0.00%	0.00%	0.19%
Commercial Real Estate [Member] \| Nonowner-Occupied [Member] \| Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 0	$ 0	$ 0	$ 5,686
Commercial Real Estate [Member] \| Nonowner-Occupied [Member] \| Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	0	0	0	4,616
Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	0	0	0	0
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 0
% of Total Class of Financing Receivable	0.09%	0.00%	0.09%	0.04%
Other Commercial [Member] \| Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 2,487	$ 0	$ 2,487	$ 1,477
Other Commercial [Member] \| Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	902	0	902	0
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	0	0	0	0
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 0
% of Total Class of Financing Receivable	0.04%	0.00%	0.05%	0.00%
Residential Real Estate [Member] \| Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 0	$ 78	$ 0	$ 78
Residential Real Estate [Member] \| Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	2,807	0	2,976	0
Construction & Land Development [Member]
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	0	0	0	0
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 0
% of Total Class of Financing Receivable	0.00%	0.00%	0.00%	0.00%
Construction & Land Development [Member] \| Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 0	$ 0	$ 0	$ 0
Construction & Land Development [Member] \| Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	0	0	0	0
Consumer [Member] \| Bankcard [Member]
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	0	0	0	0
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 0
% of Total Class of Financing Receivable	0.00%	0.00%	0.00%	0.00%
Consumer [Member] \| Bankcard [Member] \| Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 0	$ 0	$ 0	$ 0
Consumer [Member] \| Bankcard [Member] \| Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	0	0	0	0
Consumer [Member] \| Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Amortized Cost Basis Loan Modification Term Extension And Interest Rate Reduction	0	0	0	0
Amortized Cost Basis Loan Modification Term Extension And Permanent Delay	$ 0	$ 0	$ 0	$ 0
% of Total Class of Financing Receivable	0.00%	0.00%	0.00%	0.00%
Consumer [Member] \| Other Consumer [Member] \| Term Extension [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 0	$ 0	$ 0	$ 0
Consumer [Member] \| Other Consumer [Member] \| Other than insignificant payment delay [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modified	$ 0	$ 0	$ 0	$ 0

Amortized cost basis loan modification term extension and interest rate reduction.

No definition available.

Name:	ubsi_AmortizedCostBasisLoanModificationTermExtensionAndInterestRateReduction
Namespace Prefix:	ubsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost basis loan modification term extension and permanent delay.

+ References

No definition available.

+ Details

Name:	ubsi_AmortizedCostBasisLoanModificationTermExtensionAndPermanentDelay
Namespace Prefix:	ubsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

- Definition

Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=ubsi_OtherThanInsignificantPaymentDelayMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ubsi_OwnerOccupiedCommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ubsi_NonownerOccupiedCommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ubsi_BankCardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ubsi_OtherConsumerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: