Investment Securities (Summary Of Gross Realized Gains And Losses On Calls And Sales Of Held To Maturity Securities Included In Earnings) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Investments [Line Items]
Gross realized gains	$ 352	$ 1	$ 1,297
Gross realized losses	$ 0	$ 0	$ 39

Gross realized losses on calls and sales of held to maturity securities included in earnings as a result of those calls and sales.

No definition available.

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