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Mergers and Acquisitions - Summary of Fair Value of Net Assets that Wesbanco Acquired from ESB (Parenthetical) (Detail) (ESB Financial Corporation [Member], USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
ESB Financial Corporation [Member]
  
Business Acquisition [Line Items]  
Recievables from sale of available-for-sale securities $ 560.7wsbc_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedReceivablesOnSaleOfAvailableForSaleSecurities
/ us-gaap_BusinessAcquisitionAxis
= wsbc_EsbFinancialCorporationMember