Federal Home Loan Bank Advances, Other Borrowings and Subordinated Notes Federal Home Loan Bank Advances, Other Borrowings and Subordinated Notes (Summary of Debt) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Debt Disclosure [Abstract]
Federal Home Loan Bank advances	$ 416,036	$ 733,050	$ 387,672
Other borrowings:
Notes payable	0us-gaap_NotesPayable	0us-gaap_NotesPayable	182us-gaap_NotesPayable
Securities sold under repurchase agreements	50,076	48,566	211,692
Other	18,689us-gaap_OtherLongTermDebt	18,822us-gaap_OtherLongTermDebt	19,212us-gaap_OtherLongTermDebt
Secured borrowings	118,241us-gaap_SecuredDebt	129,077us-gaap_SecuredDebt	0us-gaap_SecuredDebt
Total other borrowings	187,006us-gaap_OtherBorrowings	196,465us-gaap_OtherBorrowings	231,086us-gaap_OtherBorrowings
Subordinated notes	140,000us-gaap_SubordinatedDebt	140,000us-gaap_SubordinatedDebt	0us-gaap_SubordinatedDebt
Total Federal Home Loan Bank advances, other borrowings and subordinated notes	$ 743,042wtfc_DebtCurrentandNoncurrent	$ 1,069,515wtfc_DebtCurrentandNoncurrent	$ 618,758wtfc_DebtCurrentandNoncurrent

Federal Home Loan Bank Advances, Other Borrowings and Subordinated Notes Federal Home Loan Bank Advances, Other Borrowings and Subordinated Notes (Summary of Debt) (Details) (USD $)
In Thousands, unless otherwise specified

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2014

Debt Disclosure [Abstract]

Federal Home Loan Bank advances

$ 416,036us-gaap_FederalHomeLoanBankAdvancesLongTerm

$ 733,050us-gaap_FederalHomeLoanBankAdvancesLongTerm

$ 387,672us-gaap_FederalHomeLoanBankAdvancesLongTerm

Other borrowings:

Notes payable

0us-gaap_NotesPayable

182us-gaap_NotesPayable

Securities sold under repurchase agreements

50,076us-gaap_SecuritiesSoldUnderAgreementsToRepurchase

48,566us-gaap_SecuritiesSoldUnderAgreementsToRepurchase

211,692us-gaap_SecuritiesSoldUnderAgreementsToRepurchase

Other

18,689us-gaap_OtherLongTermDebt

18,822us-gaap_OtherLongTermDebt

19,212us-gaap_OtherLongTermDebt

Secured borrowings

118,241us-gaap_SecuredDebt

129,077us-gaap_SecuredDebt

0us-gaap_SecuredDebt

Total other borrowings

187,006us-gaap_OtherBorrowings

196,465us-gaap_OtherBorrowings

231,086us-gaap_OtherBorrowings

Subordinated notes

140,000us-gaap_SubordinatedDebt

0us-gaap_SubordinatedDebt

Total Federal Home Loan Bank advances, other borrowings and subordinated notes

$ 743,042wtfc_DebtCurrentandNoncurrent

$ 1,069,515wtfc_DebtCurrentandNoncurrent

$ 618,758wtfc_DebtCurrentandNoncurrent

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Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

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-Publisher FASB

-Name Accounting Standards Codification

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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Including both current and noncurrent portions, carrying amount as of the balance sheet date of other forms of debt not elsewhere specified in the taxonomy with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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-Glossary Repurchase Agreement Accounted for as a Collateralized Borrowing

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Debt, Current and Noncurrent

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