Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

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- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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- Definition

Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after 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 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Common securities proportion to junior subordinated debentures.

+ References

No definition available.

+ Details

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- Definition

Consecutive quarters of deferred payment

+ References

No definition available.

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- Definition

Debt, Hedge Adjusted Weighted Average Interest Rate

+ References

No definition available.

+ Details

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Namespace Prefix:	wtfc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Derivative Contracts

+ References

No definition available.

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- Definition

Ownership interest percentage in unconsolidated subsidiary trusts.

+ References

No definition available.

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- Definition

Trust preferred securities proportion to junior subordinated debentures.

+ References

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+ Details

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Junior Subordinated Debentures (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified				9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013 Forward Starting Interest Rate Cap [Member]
Subordinated Borrowing [Line Items]
Percentage ownership interest in subsidiary trusts	100.00%
Common securities, approximate percentage of junior subordinated debentures	3.00%
Trust preferred securities, approximate percentage of junior subordinated debentures	97.00%
Junior subordinated debentures	$ 249,493	$ 249,493	$ 249,493
Debt, Weighted Average Interest Rate	2.44%
Notional Amount	$ 225,000			$ 90,000
Debt, Hedge Adjusted Weighted Average Interest Rate	3.25%
Number of Derivative Contracts				2
Consecutive quarters of deferred payment	20