Deposits (Summary Of Deposits) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Deposits
Non-interest bearing, Balance	$ 1,631,709	$ 1,201,194	$ 1,042,730
NOW, Balance	1,633,752	1,561,507	1,551,749
Wealth management deposits, Balance	730,315	658,660	710,435
Money market, Balance	2,190,117	1,759,866	1,746,168
Savings, Balance	867,483	744,534	713,823
Time certificates of deposit, Balance	5,252,632	4,877,912	5,197,334
Total deposits	$ 12,306,008	$ 10,803,673	$ 10,962,239
Non-interest bearing, Mix	13.00%	11.00%	10.00%
NOW, Mix	13.00%	15.00%	14.00%
Wealth management deposits, Mix	6.00%	6.00%	6.00%
Money market, Mix	18.00%	16.00%	16.00%
Savings, Mix	7.00%	7.00%	7.00%
Time certificates of deposit, Mix	43.00%	45.00%	47.00%
Total deposits, Mix	100.00%	100.00%	100.00%

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Chapter 13

-Paragraph 37, 38, 39

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

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

+ Details

Name:	us-gaap_Deposits
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DepositsAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of deposits in accounts that offer many of the same services as checking accounts although transactions may be somewhat more limited, share some of the characteristics of a money market fund and are insured by the Federal government, also known as money market accounts.

+ References

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Chapter V

-Section 563c.102

-Paragraph 14

-Subparagraph a(i)

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

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

+ Details

Name:	us-gaap_DepositsMoneyMarketDeposits
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deposits in interest-bearing transaction accounts at banks or savings and loans, that are restricted in regard to ownership and can usually only be held by individuals, nonprofit entities and governments. Negotiable order of withdrawal accounts differ from money market demand accounts as they typically have higher reserve requirements and no limit on the number of checks that can be written.

+ References

+ Details

Name:	us-gaap_DepositsNegotiableOrderOfWithdrawalNOW
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of interest bearing deposits with no stated maturity, which may include passbook and statement savings accounts and money-market deposit accounts (MMDAs).

+ References

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Chapter 13

-Paragraph 6

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

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

+ Details

Name:	us-gaap_DepositsSavingsDeposits
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate amount of all domestic and foreign noninterest-bearing deposits liabilities held by the entity.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

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

+ Details

Name:	us-gaap_NoninterestBearingDepositLiabilities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The aggregate amount of time deposits, including certificates of deposits, individual retirement accounts and open accounts.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

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

+ Details

Name:	us-gaap_TimeDeposits
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Deposits money market deposits, percentage

+ Details

Name:	wtfc_DepositsMoneyMarketDepositsPercentage
Namespace Prefix:	wtfc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Deposits negotiable order of withdrawal NOW, percentage

+ Details

Name:	wtfc_DepositsNegotiableOrderOfWithdrawalNowPercentage
Namespace Prefix:	wtfc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Deposits, Percentage

+ Details

Name:	wtfc_DepositsPercentage
Namespace Prefix:	wtfc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Deposits savings deposits, percentage

+ Details

Name:	wtfc_DepositsSavingsDepositsPercentage
Namespace Prefix:	wtfc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Non-interest bearing, percentage

+ Details

Name:	wtfc_NonInterestBearingPercentage
Namespace Prefix:	wtfc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Time deposits, percentage

+ Details

Name:	wtfc_TimeDepositsPercentage
Namespace Prefix:	wtfc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Wealth management deposits

+ Details

Name:	wtfc_WealthManagementDeposits
Namespace Prefix:	wtfc
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Wealth management deposits, percentage

+ Details

Name:	wtfc_WealthManagementDepositsPercentage
Namespace Prefix:	wtfc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant