Loans and the Allowance for Credit Losses - Additional Information (Detail)					3 Months Ended		9 Months Ended	12 Months Ended
	Jan. 01, 2020 USD ($)	Nov. 22, 2019 USD ($)	Aug. 20, 2018 USD ($)	Apr. 05, 2018 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($) Contract Loan	Dec. 31, 2019 USD ($) Contract	Dec. 31, 2018 USD ($)
Financing Receivable, Recorded Investment [Line Items]
Net deferred loan income (costs)								$ 6,200,000	$ (4,800,000)
Un-accreted discount on purchased loans from acquisitions								39,400,000	51,900,000
Recognition on retained earnings								$ 101,960,000	11,065,000	$ 7,597,000
Percentage of national unemployment projection								6.60%
Expected average percentage of national unemployment in future								6.20%
Calculation period of reversion								1 year
Reserve on accrued interest related to CARES Act								$ 300,000
Accrued interest receivable for loans								54,700,000
Accrued interest receivable for loans related to CARES Act								25,600,000
Aggregate amount of residential real estate, home equity and consumer loans classified as substandard								27,700,000	28,300,000
Internally assigned loan grades to residential real estate, home equity and consumer loans								4,100,000	5,100,000
Unfunded commercial loan commitments								$ 28,700,000	15,600,000
Loans acquired with deteriorated credit quality									$ 14,513,000
Number of restructured contracts greater than $0 million | Contract								0	0
Threshold for TDR								$ 1,000,000.0	$ 1,000,000.0
Accruing and non accrual TDR permitted interest-only payment period								6 months
Unfunded commitments to debtors for impaired loans								$ 900,000	3,300,000
Number of loans modified | Loan								3,553
Total loan amount modified CARES Act								$ 2,200,000,000
Loan amount remaining in deferral period CARES Act								$ 200,000,000
Description of deferred payments to customers impacted by the COVID-19 pandemic								Wesbanco originally offered three to six months of deferred payments to commercial and retail customers impacted by the COVID-19 pandemic depending on the type of loan and the industry for commercial loans. In the fourth quarter, Wesbanco offered up to an additional twelve months of deferred payments to certain commercial loan customers, predominantly in the hospitality industry, based on specific criteria related to the borrower, the underlying property and the potential for guarantors / co-borrowers.
Other real estate owned								$ 504,000	4,062,000
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Recognition on retained earnings								9,065,000	1,400,000	1,612,000
Loans acquired with deteriorated credit quality									4,104,000
Other real estate owned								100,000	600,000
Foreclosure proceedings in process on residential real estate loans								4,100,000	8,100,000
ASU 2016-13 [Member]
Financing Receivable, Recorded Investment [Line Items]
Adjustment for loan credit losses	$ 6,700,000							6,700,000
Revision of Prior Period, Accounting Standards Update, Adjustment [Member] | ASU 2016-13 [Member]
Financing Receivable, Recorded Investment [Line Items]
Recognition on retained earnings	41,400,000							41,442,000
Revision of Prior Period, Accounting Standards Update, Adjustment [Member] | ASU 2016-13 [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Recognition on retained earnings								5,630,000
Farmers Capital Bank Corporation [Member]
Financing Receivable, Recorded Investment [Line Items]
Un-accreted discount on purchased loans from acquisitions								9,800,000
Portfolio loans, net of unearned income			$ 1,064,800,000
Preliminary fair value of acquired loans			1,025,800,000
Book Value of 310-20 loans			988,300,000
Fair market value adjustment of acquired retained loans			26,000,000.0
Loans acquired with deteriorated credit quality			5,300,000					2,400,000
Loans acquired with deteriorated credit quality, fair value			4,600,000
Loans acquired with deteriorated credit quality outstanding customer balance								2,800,000
Acquired impaired loans allowances for credit losses								300,000
Acquired loans, sold book value						$ 45,200,000
Acquired loans, sold						$ 32,900,000
Farmers Capital Bank Corporation [Member] | Cost Recovery Method [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality, fair value			$ 2,400,000
Farmers Capital Bank Corporation [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality outstanding customer balance								300,000
Old Line Bancshares, Inc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Un-accreted discount on purchased loans from acquisitions								22,100,000
Portfolio loans, net of unearned income		$ 2,570,000,000.0
Preliminary fair value of acquired loans		2,514,061,000
Book Value of 310-20 loans		2,544,400,000
Fair market value adjustment of acquired retained loans		28,900,000
Loans acquired with deteriorated credit quality		25,600,000						18,400,000
Loans acquired with deteriorated credit quality, fair value		18,700,000
Loans acquired with deteriorated credit quality outstanding customer balance								18,700,000
Acquired impaired loans allowances for credit losses	6,100,000							5,500,000
Acquired loans, sold book value					$ 56,600,000
Acquired loans, sold					$ 36,400,000
Old Line Bancshares, Inc. [Member] | Cost Recovery Method [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality, fair value		$ 4,000,000.0
Old Line Bancshares, Inc. [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality outstanding customer balance								1,400,000
First Sentry Bancshares, Inc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Un-accreted discount on purchased loans from acquisitions								2,400,000
Portfolio loans, net of unearned income				$ 465,900,000
Preliminary fair value of acquired loans				447,279,000
Book Value of 310-20 loans				429,300,000
Fair market value adjustment of acquired retained loans				9,700,000
Loans acquired with deteriorated credit quality				5,100,000				900,000
Loans acquired with deteriorated credit quality, fair value				2,300,000
Loans acquired with deteriorated credit quality outstanding customer balance								1,000,000.0
Acquired impaired loans allowances for credit losses	$ 600,000							500,000
Acquired loans, sold book value							$ 21,700,000
Acquired loans, sold							$ 15,700,000
First Sentry Bancshares, Inc. [Member] | Cost Recovery Method [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality, fair value				$ 700,000
First Sentry Bancshares, Inc. [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans acquired with deteriorated credit quality outstanding customer balance								200,000
PPP Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Net deferred loan income (costs)								13,800,000
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Recognition on retained earnings								3,918,000	2,714,000	$ 3,430,000
Loans acquired with deteriorated credit quality									$ 883,000
Commercial and Industrial [Member] | Maximum [Member]
Financing Receivable, Recorded Investment [Line Items]
Annual sales of borrowers								100,000,000
Commercial and Industrial [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member] | ASU 2016-13 [Member]
Financing Receivable, Recorded Investment [Line Items]
Recognition on retained earnings								$ 22,357,000