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

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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 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

+ Details

Name:	us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_SubordinatedBorrowingLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Tier 1 Risk Based Capital as defined in the regulations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 505

-Section 50

-Paragraph 1H

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 505

-Section 50

-Paragraph 1

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826

+ Details

Name:	us-gaap_TierOneRiskBasedCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Tier 2 risk-based capital as defined in the regulations.

+ References

No definition available.

+ Details

Name:	us-gaap_TierTwoRiskBasedCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Common securities proportion to junior subordinated debentures.

+ References

No definition available.

+ Details

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

- Definition

Consecutive quarters of deferred payment

+ References

No definition available.

+ Details

Name:	wtfc_ConsecutiveQuartersOfDeferredPayment
Namespace Prefix:	wtfc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt, Hedge Adjusted Weighted Average Interest Rate

+ References

No definition available.

+ Details

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

- Definition

Ownership interest percentage in unconsolidated subsidiary trusts.

+ References

No definition available.

+ Details

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

- Definition

Trust preferred securities proportion to junior subordinated debentures.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_JuniorSubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	wtfc_InterestRateDerivativesByTypeAxis=wtfc_CashFlowHedgeofJuniorSubordinatedDebenturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Junior Subordinated Debentures (Narrative) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
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	$ 249,493,000	$ 249,493,000	$ 249,493,000
Consecutive quarters of deferred payment	20
Junior Subordinated Debt
Subordinated Borrowing [Line Items]
Debt, weighted average interest rate	2.46%
Debt, Hedge Adjusted Weighted Average Interest Rate	3.22%
Tier One Risk Based Capital	60,500,000
Tier Two Risk Based Capital	181,500,000
Cash Flow Hedge of Junior Subordinated Debentures \| Cash Flow Hedging \| Designated as Hedging Instrument \| Interest Rate Swaps and Caps
Subordinated Borrowing [Line Items]
Notional amount	$ 225,000,000