Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The interim consolidated financial statements of Wintrust Financial Corporation and its subsidiaries (collectively, “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 interim consolidated financial statements. The accompanying interim 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 interim 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, 2024 (“2024 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 credit losses, including the allowance for loan losses, the allowance for unfunded commitment losses and the allowance for held-to-maturity securities losses, 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 2024 Form 10-K. In preparation of these financial statements, subsequent events were evaluated through the time the financial statements were issued. Financial statements are considered issued when they are widely distributed to all shareholders and other financial statement users or filed with the SEC.
Recent Accounting Developments	Income Tax Disclosures In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures,” to enhance the transparency and decision usefulness of income tax disclosures. This ASU requires annually that all entities disclose increasingly disaggregated information on amount of income taxes paid. Further, this ASU requires annually that all public entities must disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a specific quantitative threshold. This guidance is effective for fiscal years beginning after December 15, 2024, and is to be applied either on a prospective basis or retrospective basis. Early adoption is permitted. The Company expects adoption of this standard will expand income tax disclosures within the consolidated financial statements. Compensation – Scope Application of Profits Interest and Similar Awards In March 2024, the FASB issued ASU No. 2024-01, “Compensation – Stock Compensation (Topic 718): Scope Application of Profits Interest and Similar Awards” which clarifies the guidance by providing an illustrative example to demonstrate how an entity should apply the scope guidance in Topic 718 when determining whether profits interest and similar awards should be accounted for in accordance with Topic 718. For public business entities, this guidance is effective for fiscal years beginning after December 15, 2024, including interim periods therein, and is to be applied either on a prospective basis or retrospective basis. Early adoption is permitted. Adoption of this standard did not impact the Company’s consolidated financial statements. Disaggregation of Income Statement Expenses In November 2024, the FASB issued ASU No. 2024-03, “Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses,” which requires public business entities to disclose additional information about specific expense categories including employee compensation, depreciation, intangible asset amortization, etc., as well as qualitative descriptions of certain expenses, in the notes to the financial statements. This guidance is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. The guidance is to be applied either prospectively or retrospectively. Early adoption is permitted. The Company is currently evaluating the impact of adopting this new guidance on the consolidated financial statements. Induced Conversions of Convertible Debt Instruments In November 2024, the FASB issued ASU No. 2024-04, “Debt – Debt with Conversion and Other Options (Subtopic 470-20): Induced Conversions of Convertible Debt Instruments” to clarify the requirements for determining whether certain settlements of convertible debt instruments should be accounted for as an induced conversion. This guidance is effective for fiscal years beginning after December 15, 2025, including interim periods therein, and is to be applied either on a prospective basis or retrospective basis. Early adoption is permitted. Adoption of this standard is expected to have no impact on the Company’s consolidated financial statements. Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity In May 2025, the FASB issued ASU No. 2025-03, “Business Combinations (Topic 805) and Consolidation (Topic 810): Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity” which requires an entity involved in an acquisition transaction affected by primarily exchanging equity interests when the legal acquirer is a variable interest entity that meets the definition of a business, to consider specific factors when determining which entity is the accounting acquirer. This guidance is effective for fiscal years beginning after December 15, 2026, including interim periods therein, and is to be applied on a prospective basis to any acquisition transaction that occurs after the initial application date. Early adoption is permitted. The Company is currently evaluating the impact of adopting this new guidance on the consolidated financial statements.
Cash and Cash Equivalents	For purposes of the Consolidated Statements of Cash Flows, the Company considers cash and cash equivalents to include cash on hand, cash items in the process of collection, non-interest bearing amounts due from correspondent banks, federal funds sold and securities purchased under resale agreements with original maturities of three months or less. These items are included within the Company’s Consolidated Statements of Condition as cash and due from banks, and federal funds sold and securities purchased under resale agreements.

Basis of Presentation (Policies)

6 Months Ended

Jun. 30, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The interim consolidated financial statements of Wintrust Financial Corporation and its subsidiaries (collectively, “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 interim consolidated financial statements.

The accompanying interim 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 interim 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, 2024 (“2024 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 credit losses, including the allowance for loan losses, the allowance for unfunded commitment losses and the allowance for held-to-maturity securities losses, 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 2024 Form 10-K. In preparation of these financial statements, subsequent events were evaluated through the time the financial statements were issued. Financial statements are considered issued when they are widely distributed to all shareholders and other financial statement users or filed with the SEC.

Recent Accounting Developments

Income Tax Disclosures

In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures,” to enhance the transparency and decision usefulness of income tax disclosures. This ASU requires annually that all entities disclose increasingly disaggregated information on amount of income taxes paid. Further, this ASU requires annually that all public entities must disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a specific quantitative threshold. This guidance is effective for fiscal years beginning after December 15, 2024, and is to be applied either on a prospective basis or retrospective basis. Early adoption is permitted. The Company expects adoption of this standard will expand income tax disclosures within the consolidated financial statements.

Compensation – Scope Application of Profits Interest and Similar Awards

In March 2024, the FASB issued ASU No. 2024-01, “Compensation – Stock Compensation (Topic 718): Scope Application of Profits Interest and Similar Awards” which clarifies the guidance by providing an illustrative example to demonstrate how an entity should apply the scope guidance in Topic 718 when determining whether profits interest and similar awards should be accounted for in accordance with Topic 718. For public business entities, this guidance is effective for fiscal years beginning after December 15, 2024, including interim periods therein, and is to be applied either on a prospective basis or retrospective basis. Early adoption is permitted. Adoption of this standard did not impact the Company’s consolidated financial statements.

Disaggregation of Income Statement Expenses

In November 2024, the FASB issued ASU No. 2024-03, “Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses,” which requires public business entities to disclose additional information about specific expense categories including employee compensation, depreciation, intangible asset amortization, etc., as well as qualitative descriptions of certain expenses, in the notes to the financial statements. This guidance is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. The guidance is to be applied either prospectively or retrospectively. Early adoption is permitted. The Company is currently evaluating the impact of adopting this new guidance on the consolidated financial statements.

Induced Conversions of Convertible Debt Instruments

In November 2024, the FASB issued ASU No. 2024-04, “Debt – Debt with Conversion and Other Options (Subtopic 470-20): Induced Conversions of Convertible Debt Instruments” to clarify the requirements for determining whether certain settlements of convertible debt instruments should be accounted for as an induced conversion. This guidance is effective for fiscal years beginning after December 15, 2025, including interim periods therein, and is to be applied either on a prospective basis or retrospective basis. Early adoption is permitted. Adoption of this standard is expected to have no impact on the Company’s consolidated financial statements.

Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity

In May 2025, the FASB issued ASU No. 2025-03, “Business Combinations (Topic 805) and Consolidation (Topic 810): Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity” which requires an entity involved in an acquisition transaction affected by primarily exchanging equity interests when the legal acquirer is a variable interest entity that meets the definition of a business, to consider specific factors when determining which entity is the accounting acquirer. This guidance is effective for fiscal years beginning after December 15, 2026, including interim periods therein, and is to be applied on a prospective basis to any acquisition transaction that occurs after the initial application date. Early adoption is permitted. The Company is currently evaluating the impact of adopting this new guidance on the consolidated financial statements.

Cash and Cash Equivalents

For purposes of the Consolidated Statements of Cash Flows, the Company considers cash and cash equivalents to include cash on hand, cash items in the process of collection, non-interest bearing amounts due from correspondent banks, federal funds sold and securities purchased under resale agreements with original maturities of three months or less. These items are included within the Company’s Consolidated Statements of Condition as cash and due from banks, and federal funds sold and securities purchased under resale agreements.