XML 105 R51.htm IDEA: XBRL DOCUMENT v2.4.1.9
Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
 12 Months Ended 0 Months Ended
Dec. 31, 2014
Security
Entity
Portfolios
Dec. 31, 2013
Security
Feb. 23, 2015
Summary Of Significant Accounting Policies [Line Items]      
Number of variable interest entity included in consolidated statements 1usbi_NumberOfVariableInterestEntity    
Instruments with an original maturity Less than 90 days    
Number of Investment portfolios 3usbi_NumberOfInvestmentPortfolios    
Number of securities held as trading securities 0usbi_NumberOfSecuritiesHeldAsTradingSecurities 0usbi_NumberOfSecuritiesHeldAsTradingSecurities  
Minimum percentage chances of tax benefit to be realized on examination 50.00%usbi_MinimumTaxBenefitLikelyOfBeingRealizedUponUltimateSettlementWithTaxAuthorityPercentage    
Tax benefit $ 0usbi_TaxBenefit    
Stock Options Granted, Number of Shares 83,400us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross    
Maximum [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Useful lives for all premises and equipment 30 years    
Minimum [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Useful lives for all premises and equipment 3 years    
Non Qualified Stock Options [Member] | Subsequent Event [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Stock Options Granted, Number of Shares     96,150us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= usbi_NonQualifiedStockOptionsMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember