Allowance for Loan Losses and Credit Quality Information - Summary of Nonaccrual and Past Due Loans (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Receivables [Abstract]
Acquired nonimpaired loans	$ 121,780	$ 145,800	$ 156,671

Loans and leases receivable acquired non impaired loans.

No definition available.

Name:	wsfs_LoansAndLeasesReceivableAcquiredNonImpairedLoans
Namespace Prefix:	wsfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant