Adjustments related to a change in the fair value of loans designated for sale.

No definition available.

Name:	ubsi_NonrecurringFairValueAdjustmentsOnLoansHeldForSale
Namespace Prefix:	ubsi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage increase to investor's indicated pricing based on historical sales prices for loans held for sale and associated derivatives.

+ References

No definition available.

+ Details

Name:	ubsi_SalesPriceOfLoansHeldForSaleIncreasePercentage
Namespace Prefix:	ubsi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

+ Details

Name:	us-gaap_FairValueAssetsLevel2ToLevel1TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

No definition available.

+ Details

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

- Definition

Amount of transfers of liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

+ Details

Name:	us-gaap_FairValueLiabilitiesLevel1ToLevel2TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of transfers of liabilities measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

+ Details

Name:	us-gaap_FairValueLiabilitiesLevel2ToLevel1TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of assets, excluding financial assets, that lack physical substance, having a limited useful life.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19190-110258

+ Details

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

- Details

Name:	us-gaap_FairValueByAssetClassAxis=ubsi_LoansHeldForSaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=ubsi_DerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers from Level 1 to Level 2 for financial assets	$ 0	$ 0
Transfers from Level 2 to Level 1 for financial assets	0	0
Transfers from Level 1 to Level 2 for financial liabilities	0	0
Transfers from Level 2 to Level 1 for financial liabilities	0	$ 0
Nonrecurring fair value adjustments on loans held for sale	0
Fair value measurement of intangible assets	$ 0		$ 0
Loans Held For Sale [Member] \| Minimum [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage		0.18%
Loans Held For Sale [Member] \| Maximum [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage		0.65%
Loans Held For Sale [Member] \| Weighted Average [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage		0.34%
Derivatives [Member] \| Minimum [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.18%
Derivatives [Member] \| Maximum [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.65%
Derivatives [Member] \| Weighted Average [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Sales price of loans held for sale increase percentage	0.34%