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v3.23.3

Segment Information - Narrative (Details) | 9 Months Ended
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Sep. 30, 2023 segment subsidiary
Segment Reporting Information [Line Items] |
Number of reportable segments | 3
Number of subsidiaries | subsidiary | 15
Community banking |
Segment Reporting Information [Line Items] |
Number of reportable segments | 1

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- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482810/280-10-50-18 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Number Of Subsidiaries + References No definition available. + Details
Name: | wtfc_NumberOfSubsidiaries
Namespace Prefix: | wtfc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |