Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 2,490,791,184
Entity Common Stock, Shares Outstanding		56,891,238
Documents Incorporated by Reference	Portions of the Proxy Statement for the Company’s Annual Meeting of Shareholders to be held on May 27, 2021 are incorporated by reference into Part III.
Amendment Flag	false
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Entity Central Index Key	0001015328
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
6.875% Fixed-Rate Non-Cumulative Perpetual Series E Preferred Stock, no par value
Entity Information [Line Items]
Title of 12(b) Security	6.875% Fixed-Rate Non-Cumulative Perpetual Series E Preferred Stock, no par value
Trading Symbol	WTFCP
Security Exchange Name	NASDAQ