Basis of Presentation	9 Months Ended
Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements of Wintrust Financial Corporation and Subsidiaries (“Wintrust” or the “Company”) presented herein are unaudited, but in the opinion of management reflect all necessary adjustments of a normal or recurring nature for a fair presentation of results as of the dates and for the periods covered by the consolidated financial statements. The accompanying consolidated financial statements are unaudited and do not include information or footnotes necessary for a complete presentation of financial condition, results of operations or cash flows in accordance with U.S. generally accepted accounting principles ("GAAP"). The unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 (“2017 Form 10-K”). Operating results reported for the period are not necessarily indicative of the results which may be expected for the entire year. Reclassifications of certain prior period amounts have been made to conform to the current period presentation. The preparation of the financial statements requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities. Management believes that the estimates made are reasonable, however, changes in estimates may be required if economic or other conditions develop differently from management’s expectations. Certain policies and accounting principles inherently have a greater reliance on the use of estimates, assumptions and judgments and as such have a greater possibility of producing results that could be materially different than originally reported. Management views critical accounting policies to be those which are highly dependent on subjective or complex judgments, estimates and assumptions, and where changes in those estimates and assumptions could have a significant impact on the financial statements. Management currently views the determination of the allowance for loan losses and the allowance for losses on lending-related commitments, loans acquired with evidence of credit quality deterioration since origination, estimations of fair value, the valuations required for impairment testing of goodwill, the valuation and accounting for derivative instruments and income taxes as the accounting areas that require the most subjective and complex judgments, and as such could be the most subject to revision as new information becomes available. Descriptions of the Company's significant accounting policies are included in Note 1 - “Summary of Significant Accounting Policies” of the 2017 Form 10-K.

Basis of Presentation

The consolidated financial statements of Wintrust Financial Corporation and Subsidiaries (“Wintrust” or the “Company”) presented herein are unaudited, but in the opinion of management reflect all necessary adjustments of a normal or recurring nature for a fair presentation of results as of the dates and for the periods covered by the consolidated financial statements.

The accompanying consolidated financial statements are unaudited and do not include information or footnotes necessary for a complete presentation of financial condition, results of operations or cash flows in accordance with U.S. generally accepted accounting principles ("GAAP"). The unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 (“2017 Form 10-K”). Operating results reported for the period are not necessarily indicative of the results which may be expected for the entire year. Reclassifications of certain prior period amounts have been made to conform to the current period presentation.

The preparation of the financial statements requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities. Management believes that the estimates made are reasonable, however, changes in estimates may be required if economic or other conditions develop differently from management’s expectations. Certain policies and accounting principles inherently have a greater reliance on the use of estimates, assumptions and judgments and as such have a greater possibility of producing results that could be materially different than originally reported. Management views critical accounting policies to be those which are highly dependent on subjective or complex judgments, estimates and assumptions, and where changes in those estimates and assumptions could have a significant impact on the financial statements. Management currently views the determination of the allowance for loan losses and the allowance for losses on lending-related commitments, loans acquired with evidence of credit quality deterioration since origination, estimations of fair value, the valuations required for impairment testing of goodwill, the valuation and accounting for derivative instruments and income taxes as the accounting areas that require the most subjective and complex judgments, and as such could be the most subject to revision as new information becomes available. Descriptions of the Company's significant accounting policies are included in Note 1 - “Summary of Significant Accounting Policies” of the 2017 Form 10-K.