2.4.0.84420 - Disclosure - Derivative Instruments and Other Financial Instruments Used For Hedging - Additional Information (Detail)truefalsefalse1false USDfalsefalse$D2013Q2YTDhttp://www.sec.gov/CIK0001011659duration2013-01-01T00:00:002013-06-30T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 3us-gaap_DerivativeInstrumentsGainLossLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Derivative Instruments, Gain (Loss) [Line Items]2false 4us-gaap_UnrealizedGainLossOnInterestRateCashFlowHedgesPretaxAccumulatedOtherComprehensiveIncomeLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse3300000033000000USD$falsetruefalsexbrli:monetaryItemTypemonetaryAmount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 46 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Income from accumulated other comprehensive income to net interest income3false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2false truefalseI2013Q2_CashFlowHedgingMemberhttp://www.sec.gov/CIK0001011659instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseCash Flow Hedges [Member]us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_CashFlowHedgingMemberus-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxisexplicitMembernanafalse0Cash Flow Hedges [Member]4true 3us-gaap_DerivativeInstrumentsGainLossLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Derivative Instruments, Gain (Loss) [Line Items]5false 4ub_WeightedAverageRemainingLifeOfCurrentlyActiveCashFlowHedgesub_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse003 years 7 months 24 daysfalsefalsefalsexbrli:durationItemTypenaWeighted average remaining life of the currently active cash flow hedges.No definition available.false0Weighted average remaining life of the currently active cash flow hedges6false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse3false USDtruefalse$I2013Q2_InterestRateSwapMember_LiborIndexedLoansMemberhttp://www.sec.gov/CIK0001011659instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseLIBOR indexed loans [Member]us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxisxbrldihttp://xbrl.org/2006/xbrldiub_LiborIndexedLoansMemberus-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxisexplicitMemberfalsefalseInterest rate swaps [Member]us-gaap_DerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_InterestRateSwapMemberus-gaap_DerivativeInstrumentRiskAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0LIBOR indexed loans [Member] | Interest rate swaps [Member]7true 3us-gaap_DerivativeInstrumentsGainLossLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Derivative Instruments, Gain (Loss) [Line Items]8false 4us-gaap_NotionalAmountOfCashFlowHedgeInstrumentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse20000000002000000000USD$falsetruefalsexbrli:monetaryItemTypemonetaryAggregate notional amount of all derivatives designated as cash flow hedging instruments. The notional amount relates to a number of currency units, shares, bushels, pounds, or other units specified in a derivative instrument.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Notional Amount -URI http://asc.fasb.org/extlink&oid=6519104 false2Derivative notional amountfalseDerivative Instruments and Other Financial Instruments Used For Hedging - Additional Information (Detail) (USD $)NoRoundingUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.unionbank.com/role/DisclosureDerivativeInstrumentsAndOtherFinancialInstrumentsUsedForHedgingAdditionalInformation18