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Cover - USD ($)
 12 Months Ended
Dec. 31, 2019
Feb. 26, 2020
Jun. 28, 2019
Entity Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2019    
Document Transition Report false    
Amendment Flag false    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2019    
Entity Central Index Key 0001015328    
Current Fiscal Year End Date --12-31    
Entity File Number 001-35077    
Entity Registrant Name Wintrust Financial Corp    
Entity Incorporation, State or Country Code IL    
Entity Tax Identification Number 36-3873352    
Entity Address, Address Line One 9700 W. Higgins Road, Suite 800    
Entity Address, City or Town Rosemont    
Entity Address, State or Province IL    
Entity Address, Postal Zip Code 60018    
City Area Code 847    
Local Phone Number 939-9000    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 4,110,584,294
Entity Common Stock, Shares Outstanding   57,373,345  
Documents Incorporated by Reference
Portions of the Proxy Statement for the Company’s Annual Meeting of Shareholders to be held on May 28, 2020 are incorporated by reference into Part III.
    
Common Stock, no par value      
Entity Information [Line Items]      
Title of 12(b) Security Common Stock, no par value    
Trading Symbol WTFC    
Security Exchange Name NASDAQ    
Series D Preferred Stock, no par value      
Entity Information [Line Items]      
Title of 12(b) Security Series D Preferred Stock, no par value    
Trading Symbol WTFCM    
Security Exchange Name NASDAQ