<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>397</ContextCount>
  <ElementCount>326</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>69</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information Document</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/DocumentAndEntityInformationDocument</Role>
      <ShortName>Document and Entity Information Document</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002500 - Statement - Balance Sheet Parenthetical (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/BalanceSheetParentheticalParentheticals</Role>
      <ShortName>Balance Sheet Parenthetical (Parentheticals)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1003000 - Statement - Consolidated Statements of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>Consolidated Statements of Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004000 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1005000 - Statement - Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/ConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1006500 - Statement - Stockholders' Equity Parenthetical (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/StockholdersEquityParentheticalParentheticals</Role>
      <ShortName>Stockholders' Equity Parenthetical (Parentheticals)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1007000 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Basis of Presentation (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/BasisOfPresentationNotes</Role>
      <ShortName>Basis of Presentation (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Earnings Per Common Share (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/EarningsPerCommonShareNotes</Role>
      <ShortName>Earnings Per Common Share (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Securities Available for Sale (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/SecuritiesAvailableForSaleNotes</Role>
      <ShortName>Securities Available for Sale (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Loans and Allowance for Loan Losses (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesNotes</Role>
      <ShortName>Loans and Allowance for Loan Losses (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Derivatives (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/DerivativesNotes</Role>
      <ShortName>Derivatives (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Fair Value Measurements (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsNotes</Role>
      <ShortName>Fair Value Measurements (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Comprehensive Income (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/ComprehensiveIncomeNotes</Role>
      <ShortName>Comprehensive Income (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Deferred Income Taxes (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/DeferredIncomeTaxesNotes</Role>
      <ShortName>Deferred Income Taxes (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Commitments and Contingencies (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.westbankiowa.com/role/CommitmentsAndContingenciesNotes</Role>
      <ShortName>Commitments and Contingencies (Notes)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Basis of Presentation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/BasisOfPresentationPolicies</Role>
      <ShortName>Basis of Presentation (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Earnings Per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/EarningsPerCommonShareTables</Role>
      <ShortName>Earnings Per Common Share (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Securities Available for Sale (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/SecuritiesAvailableForSaleTables</Role>
      <ShortName>Securities Available for Sale (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Loans and Allowance for Loan Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesTables</Role>
      <ShortName>Loans and Allowance for Loan Losses (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Derivatives (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/DerivativesTables</Role>
      <ShortName>Derivatives (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/ComprehensiveIncomeTables</Role>
      <ShortName>Comprehensive Income (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Deferred Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/DeferredIncomeTaxesTables</Role>
      <ShortName>Deferred Income Taxes (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/CommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - Basis of Presentation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/BasisOfPresentationDetails</Role>
      <ShortName>Basis of Presentation (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Earnings Per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/EarningsPerCommonShareDetails</Role>
      <ShortName>Earnings Per Common Share (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Earnings Per Common Share Stock Repurchase (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/EarningsPerCommonShareStockRepurchaseDetails</Role>
      <ShortName>Earnings Per Common Share Stock Repurchase (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Securities Available for Sale Security Type (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/SecuritiesAvailableForSaleSecurityTypeDetails</Role>
      <ShortName>Securities Available for Sale Security Type (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Securities Available for Sale Contractual Maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/SecuritiesAvailableForSaleContractualMaturitiesDetails</Role>
      <ShortName>Securities Available for Sale Contractual Maturities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Securities Available for Sale Detail of Sale of Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/SecuritiesAvailableForSaleDetailOfSaleOfSecuritiesDetails</Role>
      <ShortName>Securities Available for Sale Detail of Sale of Securities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Securities Available for Sale Gross Unrealized Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/SecuritiesAvailableForSaleGrossUnrealizedLossesDetails</Role>
      <ShortName>Securities Available for Sale Gross Unrealized Losses (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2404406 - Disclosure - Securities Available for Sale Other Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/SecuritiesAvailableForSaleOtherNarrativesDetails</Role>
      <ShortName>Securities Available for Sale Other Narratives (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Loans and Allowance for Loan Losses Schedule of Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Loans (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2405403 - Disclosure - Loans and Allowance for Loan Losses Schedule of Nonperforming Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfNonperformingLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Nonperforming Loans (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2405404 - Disclosure - Loans and Allowance for Loan Losses Schedule of Troubled Debt Restructurings by Type of Modification (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfTroubledDebtRestructuringsByTypeOfModificationDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Troubled Debt Restructurings by Type of Modification (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2405405 - Disclosure - Loans and Allowance for Loan Losses Schedule of Troubled Debt Restructured Loans that Subsequently Defaulted (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfTroubledDebtRestructuredLoansThatSubsequentlyDefaultedDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Troubled Debt Restructured Loans that Subsequently Defaulted (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2405406 - Disclosure - Loans and Allowance for Loan Losses Schedule of Impaired Loans With and Without an Allowance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfImpairedLoansWithAndWithoutAllowanceDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Impaired Loans With and Without an Allowance (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2405407 - Disclosure - Loans and Allowance for Loan Losses Schedule of Impaired Loans With and Without an Allowance 2 (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfImpairedLoansWithAndWithoutAllowance2Details</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Impaired Loans With and Without an Allowance 2 (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2405408 - Disclosure - Loans and Allowance for Loan Losses Reconciliation of Nonaccrual Loans With Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesReconciliationOfNonaccrualLoansWithImpairedLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Reconciliation of Nonaccrual Loans With Impaired Loans (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2405409 - Disclosure - Loans and Allowance for Loan Losses Schedule of Past Due Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfPastDueLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Past Due Loans (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2405410 - Disclosure - Loans and Allowance for Loan Losses Schedule of Loans By Credit Quality Indicator (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfLoansByCreditQualityIndicatorDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Loans By Credit Quality Indicator (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2405411 - Disclosure - Loans and Allowance for Loan Losses Schedule of Allowance for Loan Loss Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfAllowanceForLoanLossActivityDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Allowance for Loan Loss Activity (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2405412 - Disclosure - Loans and Allowance for Loan Losses Schedule of Allowance for Loan Losses by Impairment Method (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfAllowanceForLoanLossesByImpairmentMethodDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Allowance for Loan Losses by Impairment Method (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2405413 - Disclosure - Loans and Allowance for Loan Losses Schedule of Loans by Impairment Method (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesScheduleOfLoansByImpairmentMethodDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Schedule of Loans by Impairment Method (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2405414 - Disclosure - Loans and Allowance for Loan Losses Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/LoansAndAllowanceForLoanLossesNarrativeDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses Narrative (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Derivatives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/DerivativesDetails</Role>
      <ShortName>Derivatives (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Derivatives Pre-Tax Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/DerivativesPreTaxLossesDetails</Role>
      <ShortName>Derivatives Pre-Tax Losses (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Fair Value Measurements Recurring Basis by Level (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsRecurringBasisByLevelDetails</Role>
      <ShortName>Fair Value Measurements Recurring Basis by Level (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Fair Value Measurements Changes in Level 3 Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsChangesInLevel3SecuritiesDetails</Role>
      <ShortName>Fair Value Measurements Changes in Level 3 Securities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - Fair Value Measurements Quantitative Inputs - Recurring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsQuantitativeInputsRecurringDetails</Role>
      <ShortName>Fair Value Measurements Quantitative Inputs - Recurring (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2411405 - Disclosure - Fair Value Measurements Nonrecurring Basis by Level (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsNonrecurringBasisByLevelDetails</Role>
      <ShortName>Fair Value Measurements Nonrecurring Basis by Level (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2411406 - Disclosure - Fair Value Measurements Quantitative Inputs - Nonrecurring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsQuantitativeInputsNonrecurringDetails</Role>
      <ShortName>Fair Value Measurements Quantitative Inputs - Nonrecurring (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2411407 - Disclosure - Fair Value Measurements Carrying Amounts and Fair Values (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsCarryingAmountsAndFairValuesDetails</Role>
      <ShortName>Fair Value Measurements Carrying Amounts and Fair Values (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2411408 - Disclosure - Fair Value Measurements Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/FairValueMeasurementsNarrativeDetails</Role>
      <ShortName>Fair Value Measurements Narrative (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Comprehensive Income Changes in Accumulated Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/ComprehensiveIncomeChangesInAccumulatedOtherComprehensiveIncomeDetails</Role>
      <ShortName>Comprehensive Income Changes in Accumulated Other Comprehensive Income (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Deferred Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/DeferredIncomeTaxesDetails</Role>
      <ShortName>Deferred Income Taxes (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Commitments and Contingencies Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.westbankiowa.com/role/CommitmentsAndContingenciesNarrativeDetails</Role>
      <ShortName>Commitments and Contingencies Narrative (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - Consolidated Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2012'</Log>
    <Log type="Info">Process Flow-Through: 1002500 - Statement - Balance Sheet Parenthetical (Parentheticals)</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Consolidated Statements of Income</Log>
    <Log type="Info">Process Flow-Through: 1004000 - Statement - Consolidated Statements of Comprehensive Income</Log>
    <Log type="Info">Process Flow-Through: 1006500 - Statement - Stockholders' Equity Parenthetical (Parentheticals)</Log>
    <Log type="Info">Process Flow-Through: 1007000 - Statement - Consolidated Statements of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>wtba-20140630.xml</File>
    <File>wtba-20140630.xsd</File>
    <File>wtba-20140630_cal.xml</File>
    <File>wtba-20140630_def.xml</File>
    <File>wtba-20140630_lab.xml</File>
    <File>wtba-20140630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
