Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

Date the debt agreement requires the first payment to be made, in CCYY-MM-DD format.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

+ References

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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- Definition

Date the debt instrument was issued, in CCYY-MM-DD format.

+ References

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the normal operating cycle if longer.

+ References

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- Definition

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.

+ References

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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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- Definition

The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for repurchase agreements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)(1)(i)

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- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

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- Definition

The cash inflow from a borrowing where a lender is placed in a lien position behind debt having a higher priority of repayment (senior) in liquidation of the entity's assets or underlying collateral.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (b)

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- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

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- Definition

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13(1))

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-Section 50

-Paragraph 3

-Subparagraph (c)

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-Glossary Repurchase Agreement Accounted for as a Collateralized Borrowing

-URI http://asc.fasb.org/extlink&oid=49203159

Reference 6: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(1)(a)(i))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

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.

+ References

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Net Credit Exposure Repurchase Agreements

+ References

No definition available.

+ Details

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- Definition

Subordinated Debt Issued, Gross

+ References

No definition available.

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Namespace Prefix:	wtfc_
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Federal Home Loan Bank Advances, Other Borrowings and Subordinated Notes Federal Home Loan Bank Advances, Other Borrowings and Subordinated Notes (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended			1 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2015	Mar. 31, 2014	Dec. 15, 2014	Sep. 30, 2013	Nov. 06, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Notes payable	$ 0us-gaap_NotesPayable		0us-gaap_NotesPayable	$ 182,000us-gaap_NotesPayable
Loan agreement with unaffiliated banks			150,000,000us-gaap_LoansPayableToBank	101,000,000us-gaap_LoansPayableToBank
Securities sold under repurchase agreements	48,566,000		50,076,000	211,692,000
Net credit exposure repurchase agreements			0
Fixed rate promissory note	18,822,000us-gaap_OtherLongTermDebt		18,689,000us-gaap_OtherLongTermDebt	19,212,000us-gaap_OtherLongTermDebt
Proceeds from issuance of debt	150,000,000us-gaap_ProceedsFromIssuanceOfDebt
Secured borrowings	129,077,000us-gaap_SecuredDebt		118,241,000us-gaap_SecuredDebt	0us-gaap_SecuredDebt
Subordinated notes	140,000,000us-gaap_SubordinatedDebt		140,000,000us-gaap_SubordinatedDebt	0us-gaap_SubordinatedDebt
Subordinated debt issued, gross		140,000,000wtfc_SubordinatedDebtIssuedGross
Proceeds from issuance of subordinated notes, net		139,100,000
Unsecured Debt
Debt Instrument [Line Items]
Notes payable				182,000
Debt instrument, Frequency of periodic payment			quarterly
Loans Payable
Debt Instrument [Line Items]
Notes payable	0		0	0
Debt instrument, Issuance date			Dec. 15, 2014	Oct. 30, 2009
Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, Frequency of periodic payment			quarterly
Maximum borrowing capacity			75,000,000	100,000,000
Maturity date			Dec. 14, 2015		Dec. 15, 2014	Oct. 25, 2013	Nov. 06, 2014
Line of credit facility, Unused capacity, Commitment fee percentage			0.20%
Notes Payable to Banks
Debt Instrument [Line Items]
Loan agreement with unaffiliated banks								1,000,000
Maturity date						Jun. 01, 2015
Repayments of debt								1,000,000
Term Facility
Debt Instrument [Line Items]
Debt instrument, Frequency of periodic payment			quarterly
Loan agreement with unaffiliated banks			75,000,000
Maturity date			Jun. 15, 2020
Debt instrument, Date of first required payment			Sep. 30, 2015
Securities Sold under Agreements to Repurchase
Debt Instrument [Line Items]
Securities sold under repurchase agreements	48,600,000		50,100,000	31,700,000
Pledged financial instruments, Not separately reported, Securities for repurchase agreements			78,000,000
Borrowings From Banks And Brokers
Debt Instrument [Line Items]
Securities sold under repurchase agreements				180,000,000
Fixed Rate Promissory Note
Debt Instrument [Line Items]
Debt instrument, Frequency of periodic payment			monthly
Maturity date			Sep. 01, 2017
Debt instrument, Issuance date			Aug. 31, 2012
Fixed rate promissory note	$ 18,800,000		18,700,000	$ 19,200,000
Contractual rate			3.75%
Secured Debt
Debt Instrument [Line Items]
Contractual rate			1.6093%
Subordinated Debt
Debt Instrument [Line Items]
Maturity date			Jun. 13, 2024
Contractual rate			5.00%
Federal Funds Rate \| Unsecured Debt
Debt Instrument [Line Items]
Basis spread on variable rate				1.00%
Base Rate Loan \| Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate			0.50%
Base Rate Loan \| Base Rate \| Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate			0.50%
Base Rate Loan \| Base Rate \| Term Facility
Debt Instrument [Line Items]
Basis spread on variable rate			0.75%
Base Rate Loan \| Eurodollar Rate
Debt Instrument [Line Items]
Basis spread on variable rate			1.00%
Eurodollar Rate Loan \| London Interbank Offered Rate (LIBOR) \| Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate			1.50%
Eurodollar Rate Loan \| London Interbank Offered Rate (LIBOR) \| Term Facility
Debt Instrument [Line Items]
Basis spread on variable rate			1.75%