Loans and the Allowance for Credit Losses - Allowance for Credit Losses and Recorded Investments in Loans (Parenthetical) (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Troubled debt restructuring threshold	$ 1	$ 1

Threshold for individually evaluating commercial loans for impairment.

No definition available.

Name:	wsbc_ThresholdForIndividuallyEvaluatingCommercialLoansForImpairment
Namespace Prefix:	wsbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration