Allowance for Loan Losses and Credit Quality Information - Schedule of Allowance for Loan Losses and Loan Balances (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Allowance for loan losses
Beginning balance	$ 39,751	$ 37,089	$ 37,089
Charge-offs	(2,719)	(867)
Recoveries	632	554
Provision (credit)	2,114	907
Provision for acquired loans	48	(127)
Ending balance	39,826	37,556	39,751
Loans individually evaluated for impairment	4,836	2,803
Loans collectively evaluated for impairment	34,526	34,634
Acquired loans evaluated for impairment	464	119
Ending balance	39,826	37,556
Loans individually evaluated for impairment	56,997	33,700
Loans collectively evaluated for impairment	3,813,777	3,383,035
Acquired nonimpaired loans	675,607	354,694	724,100
Acquired impaired loans	31,247	32,284	33,614
Ending balance	4,577,628	3,803,713	4,469,216
Owner-occupied commercial
Allowance for loan losses
Beginning balance	6,588	6,670	6,670
Charge-offs	(192)	0
Recoveries	75	38
Provision (credit)	(441)	(6)
Provision for acquired loans	0	0
Ending balance	6,030	6,702	6,588
Loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	6,015	6,680
Acquired loans evaluated for impairment	15	22
Ending balance	6,030	6,702
Loans individually evaluated for impairment	4,020	1,270
Loans collectively evaluated for impairment	919,508	839,819
Acquired nonimpaired loans	156,724	49,765
Acquired impaired loans	12,040	4,603	12,122
Ending balance	1,092,292	895,457	1,078,162
Commercial mortgages
Allowance for loan losses
Beginning balance	8,915	6,487	6,487
Charge-offs	(104)	(17)
Recoveries	46	79
Provision (credit)	(518)	(37)
Provision for acquired loans	(4)	4
Ending balance	8,335	6,516	8,915
Loans individually evaluated for impairment	1,395	0
Loans collectively evaluated for impairment	6,763	6,427
Acquired loans evaluated for impairment	177	89
Ending balance	8,335	6,516
Loans individually evaluated for impairment	9,771	2,678
Loans collectively evaluated for impairment	928,925	893,036
Acquired nonimpaired loans	216,410	80,795
Acquired impaired loans	10,450	10,557	10,386
Ending balance	1,165,556	987,066	1,163,554
Construction
Allowance for loan losses
Beginning balance	2,838	3,521	3,521
Charge-offs	(14)	(26)
Recoveries	2	46
Provision (credit)	158	72
Provision for acquired loans	(23)	(4)
Ending balance	2,961	3,609	2,838
Loans individually evaluated for impairment	500	211
Loans collectively evaluated for impairment	2,397	3,398
Acquired loans evaluated for impairment	64	0
Ending balance	2,961	3,609
Loans individually evaluated for impairment	3,130	1,419
Loans collectively evaluated for impairment	225,718	194,654
Acquired nonimpaired loans	24,540	27,711
Acquired impaired loans	2,372	3,564	3,694
Ending balance	255,760	227,348	222,712
Complexity Risk
Allowance for loan losses
Beginning balance		1,010	1,010
Charge-offs		0
Recoveries		0
Provision (credit)		14
Provision for acquired loans		0
Ending balance		1,024
Loans individually evaluated for impairment		0
Loans collectively evaluated for impairment		1,024
Acquired loans evaluated for impairment		0
Ending balance		1,024
Loans individually evaluated for impairment		0
Loans collectively evaluated for impairment		0
Acquired nonimpaired loans		0
Acquired impaired loans		0
Ending balance		0
Commercial
Allowance for loan losses
Beginning balance	13,339	11,156	11,156
Charge-offs	(1,255)	(179)
Recoveries	84	110
Provision (credit)	1,949	484
Provision for acquired loans	88	(89)
Ending balance	14,205	11,482	13,339
Loans individually evaluated for impairment	1,860	1,473
Loans collectively evaluated for impairment	12,165	10,005
Acquired loans evaluated for impairment	180	4
Ending balance	14,205	11,482
Loans individually evaluated for impairment	16,767	5,278
Loans collectively evaluated for impairment	1,175,911	957,863
Acquired nonimpaired loans	141,933	107,380
Acquired impaired loans	5,256	12,600	6,183
Ending balance	1,339,867	1,083,121	1,287,731
Residential
Allowance for loan losses
Beginning balance	2,059	2,281	2,281
Charge-offs	(11)	(14)
Recoveries	120	22
Provision (credit)	(114)	(20)
Provision for acquired loans	0	0
Ending balance	2,054	2,269	2,059
Loans individually evaluated for impairment	887	911
Loans collectively evaluated for impairment	1,144	1,354
Acquired loans evaluated for impairment	23	4
Ending balance	2,054	2,269
Loans individually evaluated for impairment	14,280	15,260
Loans collectively evaluated for impairment	158,430	161,610
Acquired nonimpaired loans	85,679	73,240
Acquired impaired loans	866	955	860
Ending balance	259,255	251,065	267,028
Consumer
Allowance for loan losses
Beginning balance	6,012	5,964	5,964
Charge-offs	(1,143)	(631)
Recoveries	305	259
Provision (credit)	1,080	400
Provision for acquired loans	(13)	(38)
Ending balance	6,241	5,954	6,012
Loans individually evaluated for impairment	194	208
Loans collectively evaluated for impairment	6,042	5,746
Acquired loans evaluated for impairment	5	0
Ending balance	6,241	5,954
Loans individually evaluated for impairment	9,029	7,795
Loans collectively evaluated for impairment	405,285	336,053
Acquired nonimpaired loans	50,321	15,803
Acquired impaired loans	263	5	369
Ending balance	$ 464,898	$ 359,656	$ 450,029

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

Name:	us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of addition to allowance reserve for credit loss arising from purchase of loan and lease portfolios.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesLoansAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

+ Details

Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

+ Details

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Allowance for credit losses acquired and evaluated for impairment.

+ References

No definition available.

+ Details

Name:	wsfs_AllowanceForCreditLossesAcquiredAndEvaluatedForImpairment
Namespace Prefix:	wsfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loans and leases receivable acquired non impaired loans.

+ References

No definition available.

+ Details

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

- Definition

Provision for loan and lease losses loans acquired.

+ References

No definition available.

+ Details

Name:	wsfs_ProvisionForLoanAndLeaseLossesLoansAcquired
Namespace Prefix:	wsfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Provisions credit for loan and lease losses.

+ References

No definition available.

+ Details

Name:	wsfs_ProvisionsCreditForLoanAndLeaseLosses
Namespace Prefix:	wsfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wsfs_OwnerOccupiedCommercialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wsfs_CommercialMortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wsfs_EstimationOrComplexityRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: