Loans and the Allowance for Credit Losses - Allowance for Credit Losses and Recorded Investments in Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans individually evaluated for impairment	$ 3,701	$ 3,798
Allowance for loans collectively evaluated for impairment	40,472	40,856
Allowance for loan commitments	478wsbc_AllowanceForLoanCommitments	455wsbc_AllowanceForLoanCommitments	545wsbc_AllowanceForLoanCommitments	602wsbc_AllowanceForLoanCommitments
Total allowance for credit losses	44,651	45,109	46,028	47,970
Individually evaluated for impairment	12,544	14,313
Collectively evaluated for impairment	4,861,177	4,072,453
Total Loans	4,873,721	4,086,766
Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	5,331	5,654
Allowance for loan commitments	178	194	293	301
Total allowance for credit losses	5,509	5,848	5,298	6,357
Collectively evaluated for impairment	288,075	262,643
Total Loans	288,075	262,643
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans individually evaluated for impairment	2,828	2,765
Allowance for loans collectively evaluated for impairment	15,207	14,808
Allowance for loan commitments	18	10	9	62
Total allowance for credit losses	18,053	17,583	17,284	18,219
Individually evaluated for impairment	9,822	11,469
Collectively evaluated for impairment	1,899,047	1,671,348
Total Loans	1,908,869	1,682,817
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans individually evaluated for impairment	873	1,033
Allowance for loans collectively evaluated for impairment	8,138	8,030
Allowance for loan commitments	120	112	133	130
Total allowance for credit losses	9,131	9,175	9,975	10,055
Individually evaluated for impairment	2,722	2,844
Collectively evaluated for impairment	706,899	635,566
Total Loans	709,621	638,410
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	5,034	5,382
Allowance for loan commitments	13	9	5	5
Total allowance for credit losses	5,047	5,391	5,777	5,678
Collectively evaluated for impairment	1,239,163	928,770
Total Loans	1,239,163	928,770
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	2,497	2,329
Allowance for loan commitments	107	90	86	85
Total allowance for credit losses	2,604	2,419	2,112	2,102
Collectively evaluated for impairment	362,163	330,031
Total Loans	362,163	330,031
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	3,723	4,078
Allowance for loan commitments	42	40	19	19
Total allowance for credit losses	3,765	4,118	4,819	5,039
Collectively evaluated for impairment	365,830	244,095
Total Loans	365,830	244,095
Deposit Overdraft [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	542	575
Total allowance for credit losses	$ 542	$ 575	$ 763	$ 520

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(1)

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

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-Section 50

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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

+ References

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-Publisher FASB

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

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5074-111524

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Amount of allowance to cover probable credit losses on loan commitments.

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