Securities - Schedule of Fair Value and Amortized Cost of Available-for-sale and Held-to-maturity Securities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	$ 1,642,125	$ 912,850
Available-for-sale, Gross Unrealized Gains	16,306	11,771
Available-for-sale, Gross Unrealized Losses	(4,167)	(7,197)
Available-for-sale, Estimated Fair Value	1,654,264us-gaap_AvailableForSaleSecurities	917,424us-gaap_AvailableForSaleSecurities
Held-to-maturity, Amortized Cost	743,925us-gaap_HeldToMaturitySecurities	593,670us-gaap_HeldToMaturitySecurities
Held-to-maturity, Gross Unrealized Gains	30,004	27,285
Held-to-maturity, Gross Unrealized Losses	(1,086)	(1,338)
Held-to-maturity securities, Fair value	772,843	619,617
Total securities, Amortized Cost	2,386,050wsbc_SecuritiesAmortizedCost	1,506,520wsbc_SecuritiesAmortizedCost
Total securities, Gross Unrealized Gains	46,310us-gaap_UnrealizedGainOnSecurities	39,056us-gaap_UnrealizedGainOnSecurities
Total securities, Gross Unrealized Losses	(5,253)us-gaap_UnrealizedLossOnSecurities	(8,535)us-gaap_UnrealizedLossOnSecurities
Total securities, Estimated Fair Value	2,427,107wsbc_SecuritiesEstimatedFairValue	1,537,041wsbc_SecuritiesEstimatedFairValue
Residential Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	1,279,350	703,535
Available-for-sale, Gross Unrealized Gains	8,091	4,336
Available-for-sale, Gross Unrealized Losses	(3,996)	(6,758)
Available-for-sale, Estimated Fair Value	1,283,445	701,113
Held-to-maturity, Amortized Cost	126,935	79,004
Held-to-maturity, Gross Unrealized Gains	3,244	3,262
Held-to-maturity, Gross Unrealized Losses	(208)	(246)
Held-to-maturity securities, Fair value	129,971	82,020
Obligations of State and Political Subdivisions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	89,977	86,073
Available-for-sale, Gross Unrealized Gains	5,693	5,365
Available-for-sale, Gross Unrealized Losses	(17)	(5)
Available-for-sale, Estimated Fair Value	95,653	91,433
Held-to-maturity, Amortized Cost	610,249	507,927
Held-to-maturity, Gross Unrealized Gains	26,560	23,917
Held-to-maturity, Gross Unrealized Losses	(878)	(1,043)
Held-to-maturity securities, Fair value	635,931	530,801
Corporate Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	182,781	25,974
Available-for-sale, Gross Unrealized Gains	430	141
Available-for-sale, Gross Unrealized Losses	(121)	(119)
Available-for-sale, Estimated Fair Value	183,090	25,996
Held-to-maturity, Amortized Cost	6,741	6,739
Held-to-maturity, Gross Unrealized Gains	200	106
Held-to-maturity, Gross Unrealized Losses		(49)
Held-to-maturity securities, Fair value	6,941	6,796
Obligations of Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	79,315	86,964
Available-for-sale, Gross Unrealized Gains	1,486	1,087
Available-for-sale, Gross Unrealized Losses	(33)	(315)
Available-for-sale, Estimated Fair Value	80,768	87,736
Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	1,631,423	902,546
Available-for-sale, Gross Unrealized Gains	15,700	10,929
Available-for-sale, Gross Unrealized Losses	(4,167)	(7,197)
Available-for-sale, Estimated Fair Value	1,642,956	906,278
Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale, Amortized Cost	10,702	10,304
Available-for-sale, Gross Unrealized Gains	606	842
Available-for-sale, Estimated Fair Value	$ 11,308	$ 11,146

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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The increase (decrease), resulting in a gain, in the difference between the fair value and the carrying value, or in the comparative fair values, of securities held at each balance sheet date, that was included in earnings for the period.

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The increase (decrease), resulting in a loss, in the difference between the fair value and the carrying value, or in the comparative fair values, of securities held at each balance sheet date, that was included in earnings for the period.

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Securities amortized cost.

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Securities estimated fair value.

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