Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company has outstanding, at any time, a number of commitments to extend credit. These commitments include revolving home equity line and other credit agreements, term loan commitments and standby and commercial letters of credit. Standby and commercial letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. Standby letters of credit are contingent upon the failure of the customer to perform according to the terms of the underlying contract with the third party, while commercial letters of credit are issued specifically to facilitate commerce and typically result in the commitment being drawn on when the underlying transaction is consummated between the customer and the third party. These commitments involve, to varying degrees, elements of credit and interest rate risk in excess of the amounts recognized in the Consolidated Statements of Condition. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. The Company uses the same credit policies in making commitments as it does for on-balance sheet instruments. Commitments to extend commercial, commercial real estate and construction loans totaled $6.4 billion and $5.1 billion as of December 31, 2020 and 2019, respectively, and unused home equity lines totaled $756.2 million and $800.6 million as of December 31, 2020 and 2019, respectively. Standby and commercial letters of credit totaled $348.2 million at December 31, 2020 and $291.8 million at December 31, 2019. In addition, at December 31, 2020 and 2019, the Company had approximately $1.7 billion and $595.1 million, respectively, in commitments to fund residential mortgage loans to be sold into the secondary market. These lending commitments are also considered derivative instruments. The Company also enters into forward contracts for the future delivery of residential mortgage loans at specified interest rates to reduce the interest rate risk associated with commitments to fund loans as well as mortgage loans held-for-sale. These forward contracts are also considered derivative instruments and had contractual amounts of approximately $2.3 billion at December 31, 2020 and $837.2 million at December 31, 2019. See Note 21, “Derivative Financial Instruments,” for further discussion on derivative instruments. The Company enters into residential mortgage loan sale agreements with investors in the normal course of business. These agreements usually require certain representations concerning credit information, loan documentation, collateral and insurability. On occasion, investors have requested the Company to indemnify them against losses on certain loans or to repurchase loans which the investors believe do not comply with applicable representations. Management maintains a liability for estimated losses on loans expected to be repurchased or on which indemnification is expected to be provided and regularly evaluates the adequacy of this recourse liability based on trends in repurchase and indemnification requests, actual loss experience, known and inherent risks in the loans, and current economic conditions. The Company sold approximately $7.6 billion of mortgage loans in 2020 and $4.5 billion in 2019. The liability for estimated losses on repurchase and indemnification claims for residential mortgage loans previously sold to investors was $0.8 million and $2.4 million at December 31, 2020 and 2019, respectively, and was included in other liabilities on the Consolidated Statements of Condition. Losses charged against the liability were $187,000 in 2020 as compared to $639,000 in 2019. These losses relate to mortgages which experienced early payment and other defaults meeting certain representation and warranty recourse requirements. The Company has unfunded commitments to investment partnerships that qualify for CRA purposes totaling $28.5 million as of December 31, 2020. Of these commitments, $178,000 related to legally-binding unfunded commitments for tax-credit investments and was included within other liabilities on the consolidated statements of financial condition. The Company utilizes an out-sourced securities clearing platform and has agreed to indemnify the clearing broker of Wintrust Investments for losses that it may sustain from the customer accounts introduced by Wintrust Investments. As of December 31, 2020, the total amount of customer balances maintained by the clearing broker and subject to indemnification was approximately $16.8 million. Wintrust Investments seeks to control the risks associated with its customers’ activities by requiring customers to maintain margin collateral in compliance with various regulatory and internal guidelines. Litigation Matters In accordance with applicable accounting principles, the Company establishes an accrued liability for litigation and threatened litigation actions and proceedings when those actions present loss contingencies, which are both probable and estimable. In actions for which a loss is reasonably possible in future periods, the Company determines whether it can estimate a loss or range of possible loss. To determine whether a possible loss is estimable, the Company reviews and evaluates its material litigation on an ongoing basis, in conjunction with any outside counsel handling the matter, in light of potentially relevant factual and legal developments. This review may include information learned through the discovery process, rulings on substantive or dispositive motions, and settlement discussions. Lehman Holdings Matter On January 15, 2015, Lehman Brothers Holdings, Inc. (“Lehman Holdings”) sent a demand letter asserting that Wintrust Mortgage must indemnify it for losses arising from loans sold by Wintrust Mortgage to Lehman Brothers Bank, FSB under a Loan Purchase Agreement between Wintrust Mortgage, as successor to SGB Corporation, and Lehman Brothers Bank. The demand was the precursor for triggering the alternative dispute resolution process mandated by the U.S. Bankruptcy Court for the Southern District of New York. Lehman Holdings triggered the mandatory alternative dispute resolution process on October 16, 2015. On February 3, 2016, following an adverse ruling by the federal Court of Appeals for the Tenth Circuit concerning the applicable statute of limitations on certain Lehman Holdings claims, Lehman Holdings filed a complaint against Wintrust Mortgage and 150 other entities from which it had purchased loans in the U.S. Bankruptcy Court for the Southern District of New York. On March 16, 2016, Wintrust Mortgage participated in the court-ordered mediation, but the mediation did not result in a consensual resolution of the dispute. Lehman Holdings filed an amended complaint against Wintrust Mortgage on December 29, 2016. On March 31, 2017, Wintrust Mortgage moved to dismiss the amended complaint for lack of subject matter jurisdiction and improper venue or to transfer venue. The court heard argument on the motions on June 12, 2018. The court denied the motion to dismiss for lack of subject matter jurisdiction on August 14, 2018 and the defendants’ motion to transfer venue on October 2, 2018. Wintrust Mortgage appealed the denial of its motion to dismiss based on improper venue and the denial of its motion to transfer venue. On October 2, 2018, Lehman Holdings asked the court for permission to amend its complaints against Wintrust Mortgage and the other defendants to add loans allegedly purchased from the defendants and sold to various RMBS trusts. The court granted this request and allowed Lehman Holdings to assert the additional claims against existing defendants as a supplemental complaint. Lehman Holdings filed its supplemental complaint against Wintrust Mortgage on December 4, 2018. Wintrust Mortgage filed its response to the supplemental complaint on May 13, 2019. On October 5, 2020, Wintrust Mortgage and Lehman Holdings executed a settlement agreement to resolve the dispute for an amount that is immaterial to the company’s results of operations or financial condition. On October 15, 2020, the court entered an order dismissing the entire suit against Wintrust Mortgage with prejudice. Wintrust Mortgage Matter On October 17, 2018, a former Wintrust Mortgage employee filed a lawsuit in the Superior Court of Los Angeles County, California against Wintrust Mortgage alleging violation of California wage payment statutes on behalf of herself and all other hourly, nonexempt employees of Wintrust Mortgage in California. Wintrust Mortgage received service of the complaint on November 4, 2018. Wintrust Mortgage filed its response to the complaint on February 25, 2019. On November 1, 2019, the plaintiff’s counsel filed a letter with the California Department of Labor advising that it was initiating an action under California’s Private Attorney General Act statute based on the same alleged violations. In November 2019, the parties reached a settlement agreement. The parties executed a settlement agreement and on February 26, 2020, plaintiff moved the court for approval. A hearing on the motion to approve settlement was originally set for June 16, 2020, but the court continued the motion to September 8, 2020. On September 8, 2020, the court requested the parties make certain changes to the settlement agreement that were immaterial to the parties’ settlement terms. The parties have revised the settlement agreement consistent with the court’s recommendations and submitted the revised settlement agreement to the court for its approval. On January 27, 2021, the court entered its preliminary approval of the settlement. Notices of settlement are to be sent to class members by March 3, 2021 who will have until May 2, 2021 to opt out of the settlement. The Company has reserved an amount for this proposed settlement that is immaterial to its results of operations or financial condition. Northbrook Bank Matter On October 17, 2018, two individual plaintiffs filed suit in the Circuit Court of Cook County, Illinois against Northbrook Bank and Tamer Moumen on behalf of themselves and a class of approximately 42 investors in a hedge fund run by defendant Moumen. Plaintiffs allege that defendant Moumen ran a fraudulent Ponzi scheme and ran those funds through deposit accounts at Northbrook Bank. They allege the bank was negligent in failing to close the deposit accounts and that it intentionally aided and abetted defendant Moumen in the alleged fraud. They contend that Northbrook Bank is liable for losses in excess of $6 million. Northbrook Bank filed its motion to dismiss the complaint on January 15, 2019, which the court granted on March 5, 2019. On April 3, 2019, Plaintiffs filed an amended complaint based on similar allegations. Northbrook Bank again moved to dismiss. The court heard this motion on July 17, 2019 and once again dismissed the complaint without prejudice. Plaintiffs filed a second amended complaint on August 12, 2019. Northbrook moved to dismiss the second amended complaint. On November 6, 2019, the court dismissed the complaint with prejudice. Plaintiffs filed an appeal on December 2, 2019. After this appeal was fully briefed, on September 4, 2020, the Appellate Court for the First District of Illinois remanded the case back to the trial court for lack of appellate jurisdiction. The Appellate Court determined it did not have jurisdiction to hear the appeal because the trial court did not dismiss the suit against defendant Moumen and plaintiffs did not obtain the trial court’s consent for immediate appeal of the dismissal order against Northbrook Bank. On October 29, 2020, Plaintiffs cured the jurisdictional issue identified by the Appellate Court by dismissing defendant Moumen. Plaintiffs filed their renewed appeal on November 4, 2020. The appeal remains pending. Northbrook Bank believes plaintiffs’ allegations are legally and factually meritless and otherwise lacks sufficient information to estimate the amount of any potential liability. Wintrust Bank Matter On April 30, 2020, A.D. Sims LLC on behalf of itself and other similarly situated plaintiffs filed suit in the federal district court for the Northern District of Illinois against Wintrust Financial Corporation, Wintrust Bank, N.A., Bank of America, N.A., Cross River Bank, and an additional 4,971 named and unnamed defendants. Plaintiffs allege the defendant financial institutions failed to pay agent fees on loans issued by them under the federal CARES Act’s Payroll Protection Program (“PPP”) in violation of applicable law. Plaintiffs allege the collective damages could exceed $3.8 billion and have asked the court to require the defendants to establish, on a pro rata basis, a fund that could be used to pay agent fees due. Plaintiffs voluntarily dismissed Wintrust Financial Corporation as a defendant in this suit on June 29, 2020. On September 28, 2020, the class defendants filed an omnibus motion to dismiss the lawsuit. This motion was fully briefed on November 23, 2020. On December 27, 2020, legislation amending the CARES Act was enacted. The new legislation expressly stated that lenders do not owe fees to agents for assisting borrowers to obtain PPP loans absent a fee agreement between the lender and the agent. In light of this legislation, plaintiff asked the court to dismiss the case. On January 22, 2021, the district court entered plaintiff’s voluntary dismissal order. In addition, the Company and its subsidiaries, from time to time, are subject to pending and threatened legal action and proceedings arising in the ordinary course of business. Based on information currently available and upon consultation with counsel, management believes that the eventual outcome of any pending or threatened legal actions and proceedings described above, including our ordinary course litigation, will not have a material adverse effect on the operations or financial condition of the Company. However, it is possible that the ultimate resolution of these matters, if unfavorable, may be material to the results of operations or financial condition for a particular period.